644368621 has 8 divisors (see below), whose sum is σ = 724106880. Its totient is φ = 568940592.

The previous prime is 644368619. The next prime is 644368639. The reversal of 644368621 is 126863446.

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 644368621 - 2¹ = 644368619 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644368121) 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, 1077241 + ... + 1077838.

It is an arithmetic number, because the mean of its divisors is an integer number (90513360).

Almost surely, 2^644368621 is an apocalyptic number.

It is an amenable number.

644368621 is a deficient number, since it is larger than the sum of its proper divisors (79738259).

644368621 is a wasteful number, since it uses less digits than its factorization.

644368621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2155115.

The product of its digits is 165888, while the sum is 40.

The square root of 644368621 is about 25384.4168930468. The cubic root of 644368621 is about 863.7302456662.

The spelling of 644368621 in words is "six hundred forty-four million, three hundred sixty-eight thousand, six hundred twenty-one".