diff --git a/pkg/compiler/syscall.go b/pkg/compiler/syscall.go
index d69952f4d..3ad960b4b 100644
--- a/pkg/compiler/syscall.go
+++ b/pkg/compiler/syscall.go
@@ -5,11 +5,13 @@ import "github.com/nspcc-dev/neo-go/pkg/core/interop/interopnames"
 // All lists are sorted, keep 'em this way, please.
 var syscalls = map[string]map[string]string{
 	"binary": {
+		"Atoi":         interopnames.SystemBinaryAtoi,
 		"Base58Decode": interopnames.SystemBinaryBase58Decode,
 		"Base58Encode": interopnames.SystemBinaryBase58Encode,
 		"Base64Decode": interopnames.SystemBinaryBase64Decode,
 		"Base64Encode": interopnames.SystemBinaryBase64Encode,
 		"Deserialize":  interopnames.SystemBinaryDeserialize,
+		"Itoa":         interopnames.SystemBinaryItoa,
 		"Serialize":    interopnames.SystemBinarySerialize,
 	},
 	"blockchain": {
diff --git a/pkg/core/interop/binary/itoa.go b/pkg/core/interop/binary/itoa.go
new file mode 100644
index 000000000..b31918836
--- /dev/null
+++ b/pkg/core/interop/binary/itoa.go
@@ -0,0 +1,91 @@
+package binary
+
+import (
+	"encoding/hex"
+	"errors"
+	"math/big"
+	"strings"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/interop"
+	"github.com/nspcc-dev/neo-go/pkg/encoding/bigint"
+)
+
+var (
+	// ErrInvalidBase is returned when base is invalid.
+	ErrInvalidBase = errors.New("invalid base")
+	// ErrInvalidFormat is returned when string is not a number.
+	ErrInvalidFormat = errors.New("invalid format")
+)
+
+// Itoa converts number to string.
+func Itoa(ic *interop.Context) error {
+	num := ic.VM.Estack().Pop().BigInt()
+	base := ic.VM.Estack().Pop().BigInt()
+	if !base.IsInt64() {
+		return ErrInvalidBase
+	}
+	var s string
+	switch b := base.Int64(); b {
+	case 10:
+		s = num.Text(10)
+	case 16:
+		if num.Sign() == 0 {
+			s = "0"
+			break
+		}
+		bs := bigint.ToBytes(num)
+		reverse(bs)
+		s = hex.EncodeToString(bs)
+		if pad := bs[0] & 0xF8; pad == 0 || pad == 0xF8 {
+			s = s[1:]
+		}
+		s = strings.ToUpper(s)
+	default:
+		return ErrInvalidBase
+	}
+	ic.VM.Estack().PushVal(s)
+	return nil
+}
+
+// Atoi converts string to number.
+func Atoi(ic *interop.Context) error {
+	num := ic.VM.Estack().Pop().String()
+	base := ic.VM.Estack().Pop().BigInt()
+	if !base.IsInt64() {
+		return ErrInvalidBase
+	}
+	var bi *big.Int
+	switch b := base.Int64(); b {
+	case 10:
+		var ok bool
+		bi, ok = new(big.Int).SetString(num, int(b))
+		if !ok {
+			return ErrInvalidFormat
+		}
+	case 16:
+		changed := len(num)%2 != 0
+		if changed {
+			num = "0" + num
+		}
+		bs, err := hex.DecodeString(num)
+		if err != nil {
+			return ErrInvalidFormat
+		}
+		if changed && bs[0]&0x8 != 0 {
+			bs[0] |= 0xF0
+		}
+		reverse(bs)
+		bi = bigint.FromBytes(bs)
+	default:
+		return ErrInvalidBase
+	}
+	ic.VM.Estack().PushVal(bi)
+	return nil
+}
+
+func reverse(b []byte) {
+	l := len(b)
+	for i := 0; i < l/2; i++ {
+		b[i], b[l-i-1] = b[l-i-1], b[i]
+	}
+}
diff --git a/pkg/core/interop/binary/itoa_test.go b/pkg/core/interop/binary/itoa_test.go
new file mode 100644
index 000000000..faf189076
--- /dev/null
+++ b/pkg/core/interop/binary/itoa_test.go
@@ -0,0 +1,98 @@
+package binary
+
+import (
+	"errors"
+	"math"
+	"math/big"
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/interop"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/stretchr/testify/require"
+)
+
+func TestItoa(t *testing.T) {
+	var testCases = []struct {
+		num    *big.Int
+		base   *big.Int
+		result string
+	}{
+		{big.NewInt(0), big.NewInt(10), "0"},
+		{big.NewInt(0), big.NewInt(16), "0"},
+		{big.NewInt(1), big.NewInt(10), "1"},
+		{big.NewInt(-1), big.NewInt(10), "-1"},
+		{big.NewInt(1), big.NewInt(16), "1"},
+		{big.NewInt(7), big.NewInt(16), "7"},
+		{big.NewInt(8), big.NewInt(16), "08"},
+		{big.NewInt(65535), big.NewInt(16), "0FFFF"},
+		{big.NewInt(15), big.NewInt(16), "0F"},
+		{big.NewInt(-1), big.NewInt(16), "F"},
+	}
+
+	for _, tc := range testCases {
+		ic := &interop.Context{VM: vm.New()}
+		ic.VM.Estack().PushVal(tc.base)
+		ic.VM.Estack().PushVal(tc.num)
+		require.NoError(t, Itoa(ic))
+		require.Equal(t, tc.result, ic.VM.Estack().Pop().String())
+
+		ic = &interop.Context{VM: vm.New()}
+		ic.VM.Estack().PushVal(tc.base)
+		ic.VM.Estack().PushVal(tc.result)
+
+		require.NoError(t, Atoi(ic))
+		require.Equal(t, tc.num, ic.VM.Estack().Pop().BigInt())
+	}
+
+	t.Run("-1", func(t *testing.T) {
+		for _, s := range []string{"FF", "FFF", "FFFF"} {
+			ic := &interop.Context{VM: vm.New()}
+			ic.VM.Estack().PushVal(16)
+			ic.VM.Estack().PushVal(s)
+
+			require.NoError(t, Atoi(ic))
+			require.Equal(t, big.NewInt(-1), ic.VM.Estack().Pop().BigInt())
+		}
+	})
+}
+
+func TestItoaError(t *testing.T) {
+	var testCases = []struct {
+		num  *big.Int
+		base *big.Int
+		err  error
+	}{
+		{big.NewInt(1), big.NewInt(13), ErrInvalidBase},
+		{big.NewInt(-1), new(big.Int).Add(big.NewInt(math.MaxInt64), big.NewInt(10)), ErrInvalidBase},
+	}
+
+	for _, tc := range testCases {
+		ic := &interop.Context{VM: vm.New()}
+		ic.VM.Estack().PushVal(tc.base)
+		ic.VM.Estack().PushVal(tc.num)
+		err := Itoa(ic)
+		require.True(t, errors.Is(err, tc.err), "got: %v", err)
+	}
+}
+
+func TestAtoiError(t *testing.T) {
+	var testCases = []struct {
+		num  string
+		base *big.Int
+		err  error
+	}{
+		{"1", big.NewInt(13), ErrInvalidBase},
+		{"1", new(big.Int).Add(big.NewInt(math.MaxInt64), big.NewInt(16)), ErrInvalidBase},
+		{"1_000", big.NewInt(10), ErrInvalidFormat},
+		{"FE", big.NewInt(10), ErrInvalidFormat},
+		{"XD", big.NewInt(16), ErrInvalidFormat},
+	}
+
+	for _, tc := range testCases {
+		ic := &interop.Context{VM: vm.New()}
+		ic.VM.Estack().PushVal(tc.base)
+		ic.VM.Estack().PushVal(tc.num)
+		err := Atoi(ic)
+		require.True(t, errors.Is(err, tc.err), "got: %v", err)
+	}
+}
diff --git a/pkg/core/interop/interopnames/names.go b/pkg/core/interop/interopnames/names.go
index 93fc94366..c3021014d 100644
--- a/pkg/core/interop/interopnames/names.go
+++ b/pkg/core/interop/interopnames/names.go
@@ -2,11 +2,13 @@ package interopnames
 
 // Names of all used interops.
 const (
+	SystemBinaryAtoi                         = "System.Binary.Atoi"
 	SystemBinaryBase58Decode                 = "System.Binary.Base58Decode"
 	SystemBinaryBase58Encode                 = "System.Binary.Base58Encode"
 	SystemBinaryBase64Decode                 = "System.Binary.Base64Decode"
 	SystemBinaryBase64Encode                 = "System.Binary.Base64Encode"
 	SystemBinaryDeserialize                  = "System.Binary.Deserialize"
+	SystemBinaryItoa                         = "System.Binary.Itoa"
 	SystemBinarySerialize                    = "System.Binary.Serialize"
 	SystemBlockchainGetBlock                 = "System.Blockchain.GetBlock"
 	SystemBlockchainGetContract              = "System.Blockchain.GetContract"
@@ -69,11 +71,13 @@ const (
 )
 
 var names = []string{
+	SystemBinaryAtoi,
 	SystemBinaryBase58Decode,
 	SystemBinaryBase58Encode,
 	SystemBinaryBase64Decode,
 	SystemBinaryBase64Encode,
 	SystemBinaryDeserialize,
+	SystemBinaryItoa,
 	SystemBinarySerialize,
 	SystemBlockchainGetBlock,
 	SystemBlockchainGetContract,
diff --git a/pkg/core/interops.go b/pkg/core/interops.go
index 0d44457cf..b60dbaa54 100644
--- a/pkg/core/interops.go
+++ b/pkg/core/interops.go
@@ -9,6 +9,7 @@ package core
 
 import (
 	"github.com/nspcc-dev/neo-go/pkg/core/interop"
+	"github.com/nspcc-dev/neo-go/pkg/core/interop/binary"
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/callback"
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/contract"
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/crypto"
@@ -32,11 +33,13 @@ func SpawnVM(ic *interop.Context) *vm.VM {
 
 // All lists are sorted, keep 'em this way, please.
 var systemInterops = []interop.Function{
+	{Name: interopnames.SystemBinaryAtoi, Func: binary.Atoi, Price: 100000, ParamCount: 2},
 	{Name: interopnames.SystemBinaryBase58Decode, Func: runtimeDecodeBase58, Price: 100000, ParamCount: 1},
 	{Name: interopnames.SystemBinaryBase58Encode, Func: runtimeEncodeBase58, Price: 100000, ParamCount: 1},
 	{Name: interopnames.SystemBinaryBase64Decode, Func: runtimeDecodeBase64, Price: 100000, ParamCount: 1},
 	{Name: interopnames.SystemBinaryBase64Encode, Func: runtimeEncodeBase64, Price: 100000, ParamCount: 1},
 	{Name: interopnames.SystemBinaryDeserialize, Func: runtimeDeserialize, Price: 500000, ParamCount: 1},
+	{Name: interopnames.SystemBinaryItoa, Func: binary.Itoa, Price: 100000, ParamCount: 2},
 	{Name: interopnames.SystemBinarySerialize, Func: runtimeSerialize, Price: 100000, ParamCount: 1},
 	{Name: interopnames.SystemBlockchainGetBlock, Func: bcGetBlock, Price: 2500000,
 		RequiredFlags: smartcontract.AllowStates, ParamCount: 1},
diff --git a/pkg/interop/binary/binary.go b/pkg/interop/binary/binary.go
index e5f834cfb..a53f51ac4 100644
--- a/pkg/interop/binary/binary.go
+++ b/pkg/interop/binary/binary.go
@@ -40,3 +40,15 @@ func Base58Encode(b []byte) string {
 func Base58Decode(b []byte) []byte {
 	return nil
 }
+
+// Itoa converts num in a given base to string. Base should be either 10 or 16.
+// It uses `System.Binary.Itoa` syscall.
+func Itoa(num int, base int) string {
+	return ""
+}
+
+// Atoi converts string to a number in a given base. Base should be either 10 or 16.
+// It uses `System.Binary.Atoi` syscall.
+func Atoi(s string, base int) int {
+	return 0
+}