644906025 has 27 divisors (see below), whose sum is σ = 1155781029. Its totient is φ = 343746720.

The previous prime is 644905951. The next prime is 644906047. The reversal of 644906025 is 520609446.

The square root of 644906025 is 25395.

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

644906025 is a `hidden beast` number, since 6 + 4 + 49 + 0 + 602 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 43283241 + 601622784 = 6579^2 + 24528^2 .

It is not a de Polignac number, because 644906025 - 2²⁵ = 611351593 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 380079 + ... + 381771.

Almost surely, 2^644906025 is an apocalyptic number.

644906025 is the 25395-th square number.

644906025 is the 12698-th centered octagonal number.

It is an amenable number.

644906025 is a deficient number, since it is larger than the sum of its proper divisors (510875004).

644906025 is an equidigital number, since it uses as much as digits as its factorization.

644906025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3402 (or 1701 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The cubic root of 644906025 is about 863.9702962075.

Multiplying 644906025 by its sum of digits (36), we get a square (23216616900 = 152370²).

The spelling of 644906025 in words is "six hundred forty-four million, nine hundred six thousand, twenty-five".