644815885636 has 24 divisors (see below), whose sum is σ = 1229871271104. Its totient is φ = 294021699360.

The previous prime is 644815885633. The next prime is 644815885657. The reversal of 644815885636 is 636588518446.

It is a happy number.

It is a super-2 number, since 2×644815885636² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644815885633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 74696320 + ... + 74704951.

It is an arithmetic number, because the mean of its divisors is an integer number (51244636296).

Almost surely, 2^644815885636 is an apocalyptic number.

It is an amenable number.

644815885636 is a deficient number, since it is larger than the sum of its proper divisors (585055385468).

644815885636 is a wasteful number, since it uses less digits than its factorization.

644815885636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149401371 (or 149401369 counting only the distinct ones).

The product of its digits is 132710400, while the sum is 64.

The spelling of 644815885636 in words is "six hundred forty-four billion, eight hundred fifteen million, eight hundred eighty-five thousand, six hundred thirty-six".