644352631020 has 192 divisors, whose sum is σ = 2313716428800. Its totient is φ = 145822291200.

The previous prime is 644352631019. The next prime is 644352631037. The reversal of 644352631020 is 20136253446.

644352631020 is a `hidden beast` number, since 6 + 443 + 52 + 63 + 102 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 462100 + ... + 1225659.

It is an arithmetic number, because the mean of its divisors is an integer number (12050606400).

Almost surely, 2^644352631020 is an apocalyptic number.

644352631020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644352631020 is an abundant number, since it is smaller than the sum of its proper divisors (1669363797780).

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

644352631020 is a wasteful number, since it uses less digits than its factorization.

644352631020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1687885 (or 1687877 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 36.

Adding to 644352631020 its reverse (20136253446), we get a palindrome (664488884466).

The spelling of 644352631020 in words is "six hundred forty-four billion, three hundred fifty-two million, six hundred thirty-one thousand, twenty".