644722278916 has 9 divisors (see below), whose sum is σ = 1128266798421. Its totient is φ = 322360336512.

The previous prime is 644722278901. The next prime is 644722278931. The reversal of 644722278916 is 619872227446.

The square root of 644722278916 is 802946.

It is a perfect power (a square), and thus also a powerful number.

It is an interprime number because it is at equal distance from previous prime (644722278901) and next prime (644722278931).

It can be written as a sum of positive squares in only one way, i.e., 639696036100 + 5026242816 = 799810^2 + 70896^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 1405156 + ... + 1806628.

Almost surely, 2^644722278916 is an apocalyptic number.

644722278916 is the 802946-th square number.

It is an amenable number.

644722278916 is a deficient number, since it is larger than the sum of its proper divisors (483544519505).

644722278916 is an frugal number, since it uses more digits than its factorization.

644722278916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 802950 (or 401475 counting only the distinct ones).

The product of its digits is 16257024, while the sum is 58.

The spelling of 644722278916 in words is "six hundred forty-four billion, seven hundred twenty-two million, two hundred seventy-eight thousand, nine hundred sixteen".