644634517 has 2 divisors, whose sum is σ = 644634518. Its totient is φ = 644634516.

The previous prime is 644634511. The next prime is 644634541. The reversal of 644634517 is 715436446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 620956561 + 23677956 = 24919^2 + 4866^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644634517 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644634517.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644634511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322317258 + 322317259.

It is an arithmetic number, because the mean of its divisors is an integer number (322317259).

Almost surely, 2^644634517 is an apocalyptic number.

It is an amenable number.

644634517 is a deficient number, since it is larger than the sum of its proper divisors (1).

644634517 is an equidigital number, since it uses as much as digits as its factorization.

644634517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 241920, while the sum is 40.

The square root of 644634517 is about 25389.6537392695. The cubic root of 644634517 is about 863.8490342123.

The spelling of 644634517 in words is "six hundred forty-four million, six hundred thirty-four thousand, five hundred seventeen".