639694720 has 64 divisors (see below), whose sum is σ = 1747749600. Its totient is φ = 219322368.

The previous prime is 639694691. The next prime is 639694721. The reversal of 639694720 is 27496936.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639694721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 66915 + ... + 75874.

Almost surely, 2^639694720 is an apocalyptic number.

It is an amenable number.

639694720 is an abundant number, since it is smaller than the sum of its proper divisors (1108054880).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639694720 is a wasteful number, since it uses less digits than its factorization.

639694720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142815 (or 142803 counting only the distinct ones).

The product of its (nonzero) digits is 489888, while the sum is 46.

The square root of 639694720 is about 25292.1869358899. The cubic root of 639694720 is about 861.6368321742.

The spelling of 639694720 in words is "six hundred thirty-nine million, six hundred ninety-four thousand, seven hundred twenty".