644681726 has 16 divisors (see below), whose sum is σ = 1041937344. Its totient is φ = 297394464.

The previous prime is 644681717. The next prime is 644681759. The reversal of 644681726 is 627186446.

It is a super-2 number, since 2×644681726² = 831229055676678152, which contains 22 as substring.

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 7 ways as a sum of consecutive naturals, for example, 58556 + ... + 68688.

It is an arithmetic number, because the mean of its divisors is an integer number (65121084).

Almost surely, 2^644681726 is an apocalyptic number.

644681726 is a deficient number, since it is larger than the sum of its proper divisors (397255618).

644681726 is a wasteful number, since it uses less digits than its factorization.

644681726 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12595.

The product of its digits is 387072, while the sum is 44.

The square root of 644681726 is about 25390.5834119659. The cubic root of 644681726 is about 863.8701213309.

The spelling of 644681726 in words is "six hundred forty-four million, six hundred eighty-one thousand, seven hundred twenty-six".