638235664 has 20 divisors (see below), whose sum is σ = 1348998480. Its totient is φ = 290107040.

The previous prime is 638235659. The next prime is 638235667. The reversal of 638235664 is 466532836.

It is a self number, because there is not a number n which added to its sum of digits gives 638235664.

It is not an unprimeable number, because it can be changed into a prime (638235667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1812994 + ... + 1813345.

It is an arithmetic number, because the mean of its divisors is an integer number (67449924).

Almost surely, 2^638235664 is an apocalyptic number.

It is an amenable number.

638235664 is an abundant number, since it is smaller than the sum of its proper divisors (710762816).

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

638235664 is a wasteful number, since it uses less digits than its factorization.

638235664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3626358 (or 3626352 counting only the distinct ones).

The product of its digits is 622080, while the sum is 43.

The square root of 638235664 is about 25263.3264634727. The cubic root of 638235664 is about 860.9812416354.

The spelling of 638235664 in words is "six hundred thirty-eight million, two hundred thirty-five thousand, six hundred sixty-four".