638704638 has 48 divisors (see below), whose sum is σ = 1625800176. Its totient is φ = 178657920.

The previous prime is 638704631. The next prime is 638704657. The reversal of 638704638 is 836407836.

638704638 is a `hidden beast` number, since 6 + 3 + 8 + 7 + 0 + 4 + 638 = 666.

It is a super-2 number, since 2×638704638² = 815887229205422088, which contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 638704593 and 638704602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638704631) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 121495 + ... + 126642.

It is an arithmetic number, because the mean of its divisors is an integer number (33870837).

Almost surely, 2^638704638 is an apocalyptic number.

638704638 is an abundant number, since it is smaller than the sum of its proper divisors (987095538).

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

638704638 is a wasteful number, since it uses less digits than its factorization.

638704638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 248169 (or 248166 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 45.

The square root of 638704638 is about 25272.6064742044. The cubic root of 638704638 is about 861.1920723058.

The spelling of 638704638 in words is "six hundred thirty-eight million, seven hundred four thousand, six hundred thirty-eight".