644220973 has 8 divisors (see below), whose sum is σ = 739775520. Its totient is φ = 554831280.

The previous prime is 644220959. The next prime is 644220977. The reversal of 644220973 is 379022446.

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

It is a cyclic number.

It is not a de Polignac number, because 644220973 - 2²⁵ = 610666541 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644220977) 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, 1540990 + ... + 1541407.

It is an arithmetic number, because the mean of its divisors is an integer number (92471940).

Almost surely, 2^644220973 is an apocalyptic number.

It is an amenable number.

644220973 is a deficient number, since it is larger than the sum of its proper divisors (95554547).

644220973 is a wasteful number, since it uses less digits than its factorization.

644220973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3082427.

The product of its (nonzero) digits is 72576, while the sum is 37.

The square root of 644220973 is about 25381.5084855097. The cubic root of 644220973 is about 863.6642700839.

The spelling of 644220973 in words is "six hundred forty-four million, two hundred twenty thousand, nine hundred seventy-three".