644027904 has 180 divisors, whose sum is σ = 2015117676. Its totient is φ = 197922816.

The previous prime is 644027903. The next prime is 644027929. The reversal of 644027904 is 409720446.

644027904 is a `hidden beast` number, since 644 + 0 + 2 + 7 + 9 + 0 + 4 = 666.

It is a super-2 number, since 2×644027904² = 829543882261266432, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644027903) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 778339 + ... + 779165.

Almost surely, 2^644027904 is an apocalyptic number.

644027904 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644027904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1007558838).

644027904 is an abundant number, since it is smaller than the sum of its proper divisors (1371089772).

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

644027904 is a wasteful number, since it uses less digits than its factorization.

644027904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 877 (or 845 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 36.

The square root of 644027904 is about 25377.7048607631. The cubic root of 644027904 is about 863.5779832018.

The spelling of 644027904 in words is "six hundred forty-four million, twenty-seven thousand, nine hundred four".