644434721215 has 8 divisors (see below), whose sum is σ = 773326569600. Its totient is φ = 515544507552.

The previous prime is 644434721159. The next prime is 644434721257. The reversal of 644434721215 is 512127434446.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644434721215 - 2²¹ = 644432624063 is a prime.

It is a super-2 number, since 2×644434721215² (a number of 24 digits) 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 (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 765061 + ... + 1369009.

It is an arithmetic number, because the mean of its divisors is an integer number (96665821200).

Almost surely, 2^644434721215 is an apocalyptic number.

644434721215 is a deficient number, since it is larger than the sum of its proper divisors (128891848385).

644434721215 is a wasteful number, since it uses less digits than its factorization.

644434721215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 817361.

The product of its digits is 645120, while the sum is 43.

The spelling of 644434721215 in words is "six hundred forty-four billion, four hundred thirty-four million, seven hundred twenty-one thousand, two hundred fifteen".