644245924 has 63 divisors (see below), whose sum is σ = 1351844193. Its totient is φ = 268643088.

The previous prime is 644245919. The next prime is 644245993. The reversal of 644245924 is 429542446.

The square root of 644245924 is 25382.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 576480100 + 67765824 = 24010^2 + 8232^2 .

It is a super-2 number, since 2×644245924² = 830105621181227552, which contains 22 as substring.

Its product of digits (276480) is a multiple of the sum of its prime factors (120).

It is an unprimeable number.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 17412034 + ... + 17412070.

Almost surely, 2^644245924 is an apocalyptic number.

644245924 is the 25382-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644245924

644245924 is an abundant number, since it is smaller than the sum of its proper divisors (707598269).

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

644245924 is an frugal number, since it uses more digits than its factorization.

644245924 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120 (or 46 counting only the distinct ones).

The product of its digits is 276480, while the sum is 40.

The cubic root of 644245924 is about 863.6754199895.

The spelling of 644245924 in words is "six hundred forty-four million, two hundred forty-five thousand, nine hundred twenty-four".