644854561 has 8 divisors (see below), whose sum is σ = 695298240. Its totient is φ = 594530832.

The previous prime is 644854549. The next prime is 644854571. The reversal of 644854561 is 165458446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644854561 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644854571) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18655 + ... + 40468.

It is an arithmetic number, because the mean of its divisors is an integer number (86912280).

Almost surely, 2^644854561 is an apocalyptic number.

It is an amenable number.

644854561 is a deficient number, since it is larger than the sum of its proper divisors (50443679).

644854561 is a wasteful number, since it uses less digits than its factorization.

644854561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59975.

The product of its digits is 460800, while the sum is 43.

The square root of 644854561 is about 25393.9867094554. The cubic root of 644854561 is about 863.9473137633.

It can be divided in two parts, 6448 and 54561, that added together give a square (61009 = 247²).

The spelling of 644854561 in words is "six hundred forty-four million, eight hundred fifty-four thousand, five hundred sixty-one".