15911551881 has 27 divisors (see below), whose sum is σ = 24267634599. Its totient is φ = 10044860112.

The previous prime is 15911551867. The next prime is 15911551907. The reversal of 15911551881 is 18815511951.

The square root of 15911551881 is 126141.

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

15911551881 is a `hidden beast` number, since 1 + 5 + 9 + 11 + 551 + 8 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 15796719225 + 114832656 = 125685^2 + 10716^2 .

It is not a de Polignac number, because 15911551881 - 2¹¹ = 15911549833 is a prime.

It is a super-2 number, since 2×15911551881² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (15911551841) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 7188931 + ... + 7191143.

Almost surely, 2^15911551881 is an apocalyptic number.

15911551881 is the 126141-st square number.

15911551881 is the 63071-st centered octagonal number.

It is an amenable number.

15911551881 is a deficient number, since it is larger than the sum of its proper divisors (8356082718).

15911551881 is an frugal number, since it uses more digits than its factorization.

15911551881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4470 (or 2235 counting only the distinct ones).

The product of its digits is 72000, while the sum is 45.

The spelling of 15911551881 in words is "fifteen billion, nine hundred eleven million, five hundred fifty-one thousand, eight hundred eighty-one".