644533997 has 2 divisors, whose sum is σ = 644533998. Its totient is φ = 644533996.

The previous prime is 644533973. The next prime is 644534021. The reversal of 644533997 is 799335446.

It is a balanced prime because it is at equal distance from previous prime (644533973) and next prime (644534021).

It can be written as a sum of positive squares in only one way, i.e., 636502441 + 8031556 = 25229^2 + 2834^2 .

It is a cyclic number.

It is not a de Polignac number, because 644533997 - 2¹⁴ = 644517613 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 (644533907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322266998 + 322266999.

It is an arithmetic number, because the mean of its divisors is an integer number (322266999).

Almost surely, 2^644533997 is an apocalyptic number.

It is an amenable number.

644533997 is a deficient number, since it is larger than the sum of its proper divisors (1).

644533997 is an equidigital number, since it uses as much as digits as its factorization.

644533997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2449440, while the sum is 50.

The square root of 644533997 is about 25387.6741156018. The cubic root of 644533997 is about 863.8041309291.

The spelling of 644533997 in words is "six hundred forty-four million, five hundred thirty-three thousand, nine hundred ninety-seven".