644121075336 has 16 divisors (see below), whose sum is σ = 1610302688400. Its totient is φ = 214707025104.

The previous prime is 644121075259. The next prime is 644121075337. The reversal of 644121075336 is 633570121446.

It is not an unprimeable number, because it can be changed into a prime (644121075337) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13419189046 + ... + 13419189093.

It is an arithmetic number, because the mean of its divisors is an integer number (100643918025).

Almost surely, 2^644121075336 is an apocalyptic number.

It is an amenable number.

644121075336 is an abundant number, since it is smaller than the sum of its proper divisors (966181613064).

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

644121075336 is a wasteful number, since it uses less digits than its factorization.

644121075336 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26838378148 (or 26838378144 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 42.

The spelling of 644121075336 in words is "six hundred forty-four billion, one hundred twenty-one million, seventy-five thousand, three hundred thirty-six".