644611637 has 2 divisors, whose sum is σ = 644611638. Its totient is φ = 644611636.

The previous prime is 644611633. The next prime is 644611691. The reversal of 644611637 is 736116446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 380679121 + 263932516 = 19511^2 + 16246^2 .

It is a cyclic number.

It is not a de Polignac number, because 644611637 - 2² = 644611633 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644611637.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644611631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322305818 + 322305819.

It is an arithmetic number, because the mean of its divisors is an integer number (322305819).

Almost surely, 2^644611637 is an apocalyptic number.

It is an amenable number.

644611637 is a deficient number, since it is larger than the sum of its proper divisors (1).

644611637 is an equidigital number, since it uses as much as digits as its factorization.

644611637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72576, while the sum is 38.

The square root of 644611637 is about 25389.2031580355. The cubic root of 644611637 is about 863.8388138992.

The spelling of 644611637 in words is "six hundred forty-four million, six hundred eleven thousand, six hundred thirty-seven".