644304561 has 16 divisors (see below), whose sum is σ = 885491904. Its totient is φ = 416473344.

The previous prime is 644304523. The next prime is 644304587. The reversal of 644304561 is 165403446.

It is not a de Polignac number, because 644304561 - 2¹⁰ = 644303537 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644304511) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 556 + ... + 35901.

It is an arithmetic number, because the mean of its divisors is an integer number (55343244).

Almost surely, 2^644304561 is an apocalyptic number.

It is an amenable number.

644304561 is a deficient number, since it is larger than the sum of its proper divisors (241187343).

644304561 is a wasteful number, since it uses less digits than its factorization.

644304561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36640.

The product of its (nonzero) digits is 34560, while the sum is 33.

The square root of 644304561 is about 25383.1550639395. The cubic root of 644304561 is about 863.7016220951.

The spelling of 644304561 in words is "six hundred forty-four million, three hundred four thousand, five hundred sixty-one".