644993279 has 8 divisors (see below), whose sum is σ = 739857408. Its totient is φ = 550809720.

The previous prime is 644993273. The next prime is 644993281. The reversal of 644993279 is 972399446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644993279 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644993279.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644993273) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 168107 + ... + 171900.

It is an arithmetic number, because the mean of its divisors is an integer number (92482176).

Almost surely, 2^644993279 is an apocalyptic number.

644993279 is a deficient number, since it is larger than the sum of its proper divisors (94864129).

644993279 is a wasteful number, since it uses less digits than its factorization.

644993279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 340285.

The product of its digits is 2939328, while the sum is 53.

The square root of 644993279 is about 25396.7178784976. The cubic root of 644993279 is about 864.0092587135.

The spelling of 644993279 in words is "six hundred forty-four million, nine hundred ninety-three thousand, two hundred seventy-nine".