644899517 has 2 divisors, whose sum is σ = 644899518. Its totient is φ = 644899516.

The previous prime is 644899487. The next prime is 644899597. The reversal of 644899517 is 715998446.

644899517 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 504855961 + 140043556 = 22469^2 + 11834^2 .

It is a cyclic number.

It is not a de Polignac number, because 644899517 - 2⁸ = 644899261 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644899597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322449758 + 322449759.

It is an arithmetic number, because the mean of its divisors is an integer number (322449759).

Almost surely, 2^644899517 is an apocalyptic number.

It is an amenable number.

644899517 is a deficient number, since it is larger than the sum of its proper divisors (1).

644899517 is an equidigital number, since it uses as much as digits as its factorization.

644899517 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2177280, while the sum is 53.

The square root of 644899517 is about 25394.8718642170. The cubic root of 644899517 is about 863.9673899765.

The spelling of 644899517 in words is "six hundred forty-four million, eight hundred ninety-nine thousand, five hundred seventeen".