644632500820 has 96 divisors (see below), whose sum is σ = 1688012524800. Its totient is φ = 200894960640.

The previous prime is 644632500797. The next prime is 644632500829. The reversal of 644632500820 is 28005236446.

It is a super-2 number, since 2×644632500820² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644632500829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12011406 + ... + 12064954.

It is an arithmetic number, because the mean of its divisors is an integer number (17583463800).

Almost surely, 2^644632500820 is an apocalyptic number.

It is an amenable number.

644632500820 is an abundant number, since it is smaller than the sum of its proper divisors (1043380023980).

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

644632500820 is a wasteful number, since it uses less digits than its factorization.

644632500820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61393 (or 61391 counting only the distinct ones).

The product of its (nonzero) digits is 276480, while the sum is 40.

The spelling of 644632500820 in words is "six hundred forty-four billion, six hundred thirty-two million, five hundred thousand, eight hundred twenty".