644369641 has 2 divisors, whose sum is σ = 644369642. Its totient is φ = 644369640.

The previous prime is 644369639. The next prime is 644369651. The reversal of 644369641 is 146963446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 376360000 + 268009641 = 19400^2 + 16371^2 .

It is a cyclic number.

It is not a de Polignac number, because 644369641 - 2¹ = 644369639 is a prime.

Together with 644369639, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (644369651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322184820 + 322184821.

It is an arithmetic number, because the mean of its divisors is an integer number (322184821).

Almost surely, 2^644369641 is an apocalyptic number.

It is an amenable number.

644369641 is a deficient number, since it is larger than the sum of its proper divisors (1).

644369641 is an equidigital number, since it uses as much as digits as its factorization.

644369641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 373248, while the sum is 43.

The square root of 644369641 is about 25384.4369841050. The cubic root of 644369641 is about 863.7307014118.

The spelling of 644369641 in words is "six hundred forty-four million, three hundred sixty-nine thousand, six hundred forty-one".