639191904 has 144 divisors (see below), whose sum is σ = 1856624112. Its totient is φ = 191407104.

The previous prime is 639191897. The next prime is 639191911. The reversal of 639191904 is 409191936.

It is an interprime number because it is at equal distance from previous prime (639191897) and next prime (639191911).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2307414 + ... + 2307690.

It is an arithmetic number, because the mean of its divisors is an integer number (12893223).

Almost surely, 2^639191904 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639191904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (928312056).

639191904 is an abundant number, since it is smaller than the sum of its proper divisors (1217432208).

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

639191904 is a wasteful number, since it uses less digits than its factorization.

639191904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 389 (or 338 counting only the distinct ones).

The product of its (nonzero) digits is 52488, while the sum is 42.

The square root of 639191904 is about 25282.2448370393. The cubic root of 639191904 is about 861.4110169870.

The spelling of 639191904 in words is "six hundred thirty-nine million, one hundred ninety-one thousand, nine hundred four".