644645165 has 12 divisors (see below), whose sum is σ = 779296284. Its totient is φ = 511929216.

The previous prime is 644645159. The next prime is 644645189. The reversal of 644645165 is 561546446.

It can be written as a sum of positive squares in 2 ways, for example, as 105801796 + 538843369 = 10286^2 + 23213^2 .

It is not a de Polignac number, because 644645165 - 2⁶ = 644645101 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 93269 + ... + 99941.

It is an arithmetic number, because the mean of its divisors is an integer number (64941357).

Almost surely, 2^644645165 is an apocalyptic number.

It is an amenable number.

644645165 is a deficient number, since it is larger than the sum of its proper divisors (134651119).

644645165 is an equidigital number, since it uses as much as digits as its factorization.

644645165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6956 (or 6817 counting only the distinct ones).

The product of its digits is 345600, while the sum is 41.

The square root of 644645165 is about 25389.8634301171. The cubic root of 644645165 is about 863.8537905063.

The spelling of 644645165 in words is "six hundred forty-four million, six hundred forty-five thousand, one hundred sixty-five".