644265961 has 2 divisors, whose sum is σ = 644265962. Its totient is φ = 644265960.

The previous prime is 644265917. The next prime is 644266019. The reversal of 644265961 is 169562446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 541446361 + 102819600 = 23269^2 + 10140^2 .

It is a cyclic number.

It is not a de Polignac number, because 644265961 - 2⁷ = 644265833 is a prime.

It is not a weakly prime, because it can be changed into another prime (644265911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322132980 + 322132981.

It is an arithmetic number, because the mean of its divisors is an integer number (322132981).

Almost surely, 2^644265961 is an apocalyptic number.

It is an amenable number.

644265961 is a deficient number, since it is larger than the sum of its proper divisors (1).

644265961 is an equidigital number, since it uses as much as digits as its factorization.

644265961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 43.

The square root of 644265961 is about 25382.3947057798. The cubic root of 644265961 is about 863.6843737571.

The spelling of 644265961 in words is "six hundred forty-four million, two hundred sixty-five thousand, nine hundred sixty-one".