644754973 has 2 divisors, whose sum is σ = 644754974. Its totient is φ = 644754972.

The previous prime is 644754959. The next prime is 644754991. The reversal of 644754973 is 379457446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 475806969 + 168948004 = 21813^2 + 12998^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644754973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644754673) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322377486 + 322377487.

It is an arithmetic number, because the mean of its divisors is an integer number (322377487).

Almost surely, 2^644754973 is an apocalyptic number.

It is an amenable number.

644754973 is a deficient number, since it is larger than the sum of its proper divisors (1).

644754973 is an equidigital number, since it uses as much as digits as its factorization.

644754973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2540160, while the sum is 49.

The square root of 644754973 is about 25392.0257758218. The cubic root of 644754973 is about 863.9028369568.

The spelling of 644754973 in words is "six hundred forty-four million, seven hundred fifty-four thousand, nine hundred seventy-three".