644022868 has 24 divisors (see below), whose sum is σ = 1166235840. Its totient is φ = 310981440.

The previous prime is 644022859. The next prime is 644022881. The reversal of 644022868 is 868220446.

It is a hoax number, since the sum of its digits (40) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 644022868.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5728 + ... + 36343.

It is an arithmetic number, because the mean of its divisors is an integer number (48593160).

Almost surely, 2^644022868 is an apocalyptic number.

It is an amenable number.

644022868 is a deficient number, since it is larger than the sum of its proper divisors (522212972).

644022868 is a wasteful number, since it uses less digits than its factorization.

644022868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42207 (or 42205 counting only the distinct ones).

The product of its (nonzero) digits is 147456, while the sum is 40.

The square root of 644022868 is about 25377.6056396186. The cubic root of 644022868 is about 863.5757322693.

The spelling of 644022868 in words is "six hundred forty-four million, twenty-two thousand, eight hundred sixty-eight".