644827820856 has 32 divisors (see below), whose sum is σ = 1620422255760. Its totient is φ = 213828913152.

The previous prime is 644827820831. The next prime is 644827820867. The reversal of 644827820856 is 658028728446.

644827820856 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 644827820856.

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, 69601135 + ... + 69610398.

Almost surely, 2^644827820856 is an apocalyptic number.

It is an amenable number.

644827820856 is an abundant number, since it is smaller than the sum of its proper divisors (975594434904).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644827820856 is a wasteful number, since it uses less digits than its factorization.

644827820856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139211735 (or 139211731 counting only the distinct ones).

The product of its (nonzero) digits is 41287680, while the sum is 60.

The spelling of 644827820856 in words is "six hundred forty-four billion, eight hundred twenty-seven million, eight hundred twenty thousand, eight hundred fifty-six".