644956321 has 2 divisors, whose sum is σ = 644956322. Its totient is φ = 644956320.

The previous prime is 644956267. The next prime is 644956339. The reversal of 644956321 is 123659446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 405821025 + 239135296 = 20145^2 + 15464^2 .

It is a cyclic number.

It is not a de Polignac number, because 644956321 - 2²³ = 636567713 is a prime.

It is not a weakly prime, because it can be changed into another prime (644956381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322478160 + 322478161.

It is an arithmetic number, because the mean of its divisors is an integer number (322478161).

Almost surely, 2^644956321 is an apocalyptic number.

It is an amenable number.

644956321 is a deficient number, since it is larger than the sum of its proper divisors (1).

644956321 is an equidigital number, since it uses as much as digits as its factorization.

644956321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 155520, while the sum is 40.

The square root of 644956321 is about 25395.9902543689. The cubic root of 644956321 is about 863.9927558728.

The spelling of 644956321 in words is "six hundred forty-four million, nine hundred fifty-six thousand, three hundred twenty-one".