11981710521 has 81 divisors (see below), whose sum is σ = 19842178629. Its totient is φ = 6961719600.

The previous prime is 11981710493. The next prime is 11981710523. The reversal of 11981710521 is 12501718911.

The square root of 11981710521 is 109461.

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

11981710521 is a `hidden beast` number, since 119 + 8 + 1 + 7 + 10 + 521 = 666.

It is not a de Polignac number, because 11981710521 - 2¹³ = 11981702329 is a prime.

It is a super-2 number, since 2×11981710521² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (11981710523) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 111978550 + ... + 111978656.

Almost surely, 2^11981710521 is an apocalyptic number.

11981710521 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

11981710521 is the 109461-st square number.

11981710521 is the 54731-st centered octagonal number.

It is an amenable number.

11981710521 is a deficient number, since it is larger than the sum of its proper divisors (7860468108).

11981710521 is a wasteful number, since it uses less digits than its factorization.

11981710521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304 (or 152 counting only the distinct ones).

The product of its (nonzero) digits is 5040, while the sum is 36.

Multiplying 11981710521 by its sum of digits (36), we get a square (431341578756 = 656766²).

The spelling of 11981710521 in words is "eleven billion, nine hundred eighty-one million, seven hundred ten thousand, five hundred twenty-one".