644861952 has 416 divisors, whose sum is σ = 2359008000. Its totient is φ = 173408256.

The previous prime is 644861941. The next prime is 644861989. The reversal of 644861952 is 259168446.

It is a junction number, because it is equal to n+sod(n) for n = 644861898 and 644861907.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 37933048 + ... + 37933064.

Almost surely, 2^644861952 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 644861952, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1179504000).

644861952 is an abundant number, since it is smaller than the sum of its proper divisors (1714146048).

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

644861952 is an equidigital number, since it uses as much as digits as its factorization.

644861952 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71 (or 29 counting only the distinct ones).

The product of its digits is 414720, while the sum is 45.

The square root of 644861952 is about 25394.1322356170. The cubic root of 644861952 is about 863.9506144612.

The spelling of 644861952 in words is "six hundred forty-four million, eight hundred sixty-one thousand, nine hundred fifty-two".