647

647 is a natural number that follows 646 and precedes 648. In mathematics, 647 is a prime number. It is odd and not divisible by 3 or 5. It is congruent to 3 modulo 4, so it cannot be expressed as a sum of two squares. 647 in Roman numerals is DCXLVII. 647 can be represented in other base numeral systems as binary 1010000111, octal 1207, and hexadecimal 0x287. As a telecommunication designation, 647 is used as an area code for parts of the Toronto area in Canada, running as an overlay with 416.