4

Four.

Power of Two

2² = 4

Perfect Square

4 is a perfect square (2 × 2)

Quick Response (QR) Code

What is a QR code?

Barcode

Hexadecimal

Even

4 is even

Previous even number is 2

Next even number is 6

Octal

Cubed

Squared

Power of Two

2⁴ = 16

Binary

Roman Numerals

IV

Unix Timestamp

Thursday, 01 January 1970 00:00:04 UTC