644877387268 has 6 divisors (see below), whose sum is σ = 1128535427726. Its totient is φ = 322438693632.

The previous prime is 644877387227. The next prime is 644877387293. The reversal of 644877387268 is 862783778446.

It can be written as a sum of positive squares in only one way, i.e., 637621414144 + 7255973124 = 798512^2 + 85182^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644877387197 and 644877387206.

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 as a sum of consecutive naturals, namely, 80609673405 + ... + 80609673412.

Almost surely, 2^644877387268 is an apocalyptic number.

It is an amenable number.

644877387268 is a deficient number, since it is larger than the sum of its proper divisors (483658040458).

644877387268 is a wasteful number, since it uses less digits than its factorization.

644877387268 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161219346821 (or 161219346819 counting only the distinct ones).

The product of its digits is 606928896, while the sum is 70.

The spelling of 644877387268 in words is "six hundred forty-four billion, eight hundred seventy-seven million, three hundred eighty-seven thousand, two hundred sixty-eight".