644121276 has 24 divisors (see below), whose sum is σ = 1534928640. Its totient is φ = 210138672.

The previous prime is 644121259. The next prime is 644121281. The reversal of 644121276 is 672121446.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 570466 + ... + 571593.

It is an arithmetic number, because the mean of its divisors is an integer number (63955360).

Almost surely, 2^644121276 is an apocalyptic number.

It is an amenable number.

644121276 is an abundant number, since it is smaller than the sum of its proper divisors (890807364).

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

644121276 is a wasteful number, since it uses less digits than its factorization.

644121276 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1142113 (or 1142111 counting only the distinct ones).

The product of its digits is 16128, while the sum is 33.

The square root of 644121276 is about 25379.5444403559. The cubic root of 644121276 is about 863.6197154034.

The spelling of 644121276 in words is "six hundred forty-four million, one hundred twenty-one thousand, two hundred seventy-six".