644021822 has 16 divisors (see below), whose sum is σ = 985623552. Its totient is φ = 315531480.

The previous prime is 644021801. The next prime is 644021839. The reversal of 644021822 is 228120446.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13013 + ... + 38175.

It is an arithmetic number, because the mean of its divisors is an integer number (61601472).

Almost surely, 2^644021822 is an apocalyptic number.

644021822 is a deficient number, since it is larger than the sum of its proper divisors (341601730).

644021822 is a wasteful number, since it uses less digits than its factorization.

644021822 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25423.

The product of its (nonzero) digits is 6144, while the sum is 29.

The square root of 644021822 is about 25377.5850308890. The cubic root of 644021822 is about 863.5752647390.

The spelling of 644021822 in words is "six hundred forty-four million, twenty-one thousand, eight hundred twenty-two".