638904641 has 8 divisors (see below), whose sum is σ = 656970600. Its totient is φ = 620880768.

The previous prime is 638904611. The next prime is 638904653. The reversal of 638904641 is 146409836.

It can be written as a sum of positive squares in 4 ways, for example, as 364008241 + 274896400 = 19079^2 + 16580^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638904641 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (638904611) 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, 21635 + ... + 41783.

It is an arithmetic number, because the mean of its divisors is an integer number (82121325).

Almost surely, 2^638904641 is an apocalyptic number.

It is an amenable number.

638904641 is a deficient number, since it is larger than the sum of its proper divisors (18065959).

638904641 is a wasteful number, since it uses less digits than its factorization.

638904641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21043.

The product of its (nonzero) digits is 124416, while the sum is 41.

The square root of 638904641 is about 25276.5630772856. The cubic root of 638904641 is about 861.2819537171.

The spelling of 638904641 in words is "six hundred thirty-eight million, nine hundred four thousand, six hundred forty-one".