644165051 has 2 divisors, whose sum is σ = 644165052. Its totient is φ = 644165050.

The previous prime is 644165047. The next prime is 644165057. The reversal of 644165051 is 150561446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644165051 - 2² = 644165047 is a prime.

It is a super-2 number, since 2×644165051² = 829897225859665202, which contains 22 as substring.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 644164999 and 644165017.

It is not a weakly prime, because it can be changed into another prime (644165057) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322082525 + 322082526.

It is an arithmetic number, because the mean of its divisors is an integer number (322082526).

Almost surely, 2^644165051 is an apocalyptic number.

644165051 is a deficient number, since it is larger than the sum of its proper divisors (1).

644165051 is an equidigital number, since it uses as much as digits as its factorization.

644165051 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 14400, while the sum is 32.

The square root of 644165051 is about 25380.4068328307. The cubic root of 644165051 is about 863.6392790571.

The spelling of 644165051 in words is "six hundred forty-four million, one hundred sixty-five thousand, fifty-one".