644594131621438 has 16 divisors (see below), whose sum is σ = 969571043910144. Its totient is φ = 321404192952480.

The previous prime is 644594131621409. The next prime is 644594131621469. The reversal of 644594131621438 is 834126131495446.

It is a happy number.

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, 99173293 + ... + 105472888.

It is an arithmetic number, because the mean of its divisors is an integer number (60598190244384).

Almost surely, 2^{644594131621438} is an apocalyptic number.

644594131621438 is a deficient number, since it is larger than the sum of its proper divisors (324976912288706).

644594131621438 is a wasteful number, since it uses less digits than its factorization.

644594131621438 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 204650547.

The product of its digits is 59719680, while the sum is 61.

The spelling of 644594131621438 in words is "six hundred forty-four trillion, five hundred ninety-four billion, one hundred thirty-one million, six hundred twenty-one thousand, four hundred thirty-eight".