644726478 has 48 divisors (see below), whose sum is σ = 1478994048. Its totient is φ = 186872400.

The previous prime is 644726441. The next prime is 644726483. The reversal of 644726478 is 874627446.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 2608 + ... + 36003.

It is an arithmetic number, because the mean of its divisors is an integer number (30812376).

Almost surely, 2^644726478 is an apocalyptic number.

644726478 is an abundant number, since it is smaller than the sum of its proper divisors (834267570).

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

644726478 is a wasteful number, since it uses less digits than its factorization.

644726478 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38661 (or 38650 counting only the distinct ones).

The product of its digits is 1806336, while the sum is 48.

The square root of 644726478 is about 25391.4646682699. The cubic root of 644726478 is about 863.8901100166.

The spelling of 644726478 in words is "six hundred forty-four million, seven hundred twenty-six thousand, four hundred seventy-eight".