15991878681 has 15 divisors (see below), whose sum is σ = 23890803013. Its totient is φ = 10660493700.

The previous prime is 15991878667. The next prime is 15991878709. The reversal of 15991878681 is 18687819951.

The square root of 15991878681 is 126459.

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

It is not a de Polignac number, because 15991878681 - 2⁵ = 15991878649 is a prime.

It is a super-2 number, since 2×15991878681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15991878781) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 1131106 + ... + 1145156.

Almost surely, 2^15991878681 is an apocalyptic number.

15991878681 is the 126459-th square number.

15991878681 is the 63230-th centered octagonal number.

It is an amenable number.

15991878681 is a deficient number, since it is larger than the sum of its proper divisors (7898924332).

15991878681 is an frugal number, since it uses more digits than its factorization.

15991878681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28114 (or 14054 counting only the distinct ones).

The product of its digits is 8709120, while the sum is 63.

The spelling of 15991878681 in words is "fifteen billion, nine hundred ninety-one million, eight hundred seventy-eight thousand, six hundred eighty-one".