639626408 has 8 divisors (see below), whose sum is σ = 1199299530. Its totient is φ = 319813200.

The previous prime is 639626399. The next prime is 639626413. The reversal of 639626408 is 804626936.

It can be written as a sum of positive squares in only one way, i.e., 542051524 + 97574884 = 23282^2 + 9878^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39976643 + ... + 39976658.

Almost surely, 2^639626408 is an apocalyptic number.

It is an amenable number.

639626408 is a deficient number, since it is larger than the sum of its proper divisors (559673122).

639626408 is a wasteful number, since it uses less digits than its factorization.

639626408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79953307 (or 79953303 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 44.

The square root of 639626408 is about 25290.8364432654. The cubic root of 639626408 is about 861.6061601319.

The spelling of 639626408 in words is "six hundred thirty-nine million, six hundred twenty-six thousand, four hundred eight".