644735538120 has 64 divisors (see below), whose sum is σ = 1941090013440. Its totient is φ = 171317619200.

The previous prime is 644735538101. The next prime is 644735538131. The reversal of 644735538120 is 21835537446.

644735538120 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×644735538120² (a number of 24 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 644735538120.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9526416 + ... + 9593855.

It is an arithmetic number, because the mean of its divisors is an integer number (30329531460).

Almost surely, 2^644735538120 is an apocalyptic number.

644735538120 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644735538120 is an abundant number, since it is smaller than the sum of its proper divisors (1296354475320).

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

644735538120 is a wasteful number, since it uses less digits than its factorization.

644735538120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19120566 (or 19120562 counting only the distinct ones).

The product of its (nonzero) digits is 2419200, while the sum is 48.

The spelling of 644735538120 in words is "six hundred forty-four billion, seven hundred thirty-five million, five hundred thirty-eight thousand, one hundred twenty".