644217693 has 32 divisors (see below), whose sum is σ = 1018302720. Its totient is φ = 354585600.

The previous prime is 644217653. The next prime is 644217713. The reversal of 644217693 is 396712446.

It is not a de Polignac number, because 644217693 - 2⁸ = 644217437 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644217653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 74373 + ... + 82581.

It is an arithmetic number, because the mean of its divisors is an integer number (31821960).

Almost surely, 2^644217693 is an apocalyptic number.

It is an amenable number.

644217693 is a deficient number, since it is larger than the sum of its proper divisors (374085027).

644217693 is a wasteful number, since it uses less digits than its factorization.

644217693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8357.

The product of its digits is 217728, while the sum is 42.

The square root of 644217693 is about 25381.4438714585. The cubic root of 644217693 is about 863.6628043220.

The spelling of 644217693 in words is "six hundred forty-four million, two hundred seventeen thousand, six hundred ninety-three".