644916719 has 2 divisors, whose sum is σ = 644916720. Its totient is φ = 644916718.

The previous prime is 644916691. The next prime is 644916749. The reversal of 644916719 is 917619446.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644916719 is a prime.

It is a super-2 number, since 2×644916719² = 831835148891449922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644916749) 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, 322458359 + 322458360.

It is an arithmetic number, because the mean of its divisors is an integer number (322458360).

Almost surely, 2^644916719 is an apocalyptic number.

644916719 is a deficient number, since it is larger than the sum of its proper divisors (1).

644916719 is an equidigital number, since it uses as much as digits as its factorization.

644916719 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 47.

The square root of 644916719 is about 25395.2105523857. The cubic root of 644916719 is about 863.9750717080.

The spelling of 644916719 in words is "six hundred forty-four million, nine hundred sixteen thousand, seven hundred nineteen".