639963257 has 8 divisors (see below), whose sum is σ = 650400192. Its totient is φ = 629566000.

The previous prime is 639963251. The next prime is 639963299. The reversal of 639963257 is 752369936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639963257 - 2⁴ = 639963241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639963251) 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, 23507 + ... + 42807.

It is an arithmetic number, because the mean of its divisors is an integer number (81300024).

Almost surely, 2^639963257 is an apocalyptic number.

It is an amenable number.

639963257 is a deficient number, since it is larger than the sum of its proper divisors (10436935).

639963257 is a wasteful number, since it uses less digits than its factorization.

639963257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19839.

The product of its digits is 1837080, while the sum is 50.

The square root of 639963257 is about 25297.4950736234. The cubic root of 639963257 is about 861.7573839484.

The spelling of 639963257 in words is "six hundred thirty-nine million, nine hundred sixty-three thousand, two hundred fifty-seven".