12787312561 has 3 divisors (see below), whose sum is σ = 12787425643. Its totient is φ = 12787199480.

The previous prime is 12787312477. The next prime is 12787312567. The reversal of 12787312561 is 16521378721.

The square root of 12787312561 is 113081.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 7504930161 + 5282382400 = 86631^2 + 72680^2 .

It is not a de Polignac number, because 12787312561 - 2²¹ = 12785215409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12787312567) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 56541 + ... + 169621.

Almost surely, 2^12787312561 is an apocalyptic number.

12787312561 is the 113081-st square number.

12787312561 is the 56541-st centered octagonal number.

It is an amenable number.

12787312561 is a deficient number, since it is larger than the sum of its proper divisors (113082).

12787312561 is an frugal number, since it uses more digits than its factorization.

12787312561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 226162 (or 113081 counting only the distinct ones).

The product of its digits is 141120, while the sum is 43.

The spelling of 12787312561 in words is "twelve billion, seven hundred eighty-seven million, three hundred twelve thousand, five hundred sixty-one".