11981087581 has 2 divisors, whose sum is σ = 11981087582. Its totient is φ = 11981087580.

The previous prime is 11981087543. The next prime is 11981087597. The reversal of 11981087581 is 18578018911.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8182830681 + 3798256900 = 90459^2 + 61630^2 .

It is a cyclic number.

It is not a de Polignac number, because 11981087581 - 2⁷ = 11981087453 is a prime.

It is a super-2 number, since 2×11981087581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11981087381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5990543790 + 5990543791.

It is an arithmetic number, because the mean of its divisors is an integer number (5990543791).

Almost surely, 2^11981087581 is an apocalyptic number.

It is an amenable number.

11981087581 is a deficient number, since it is larger than the sum of its proper divisors (1).

11981087581 is an equidigital number, since it uses as much as digits as its factorization.

11981087581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 161280, while the sum is 49.

The spelling of 11981087581 in words is "eleven billion, nine hundred eighty-one million, eighty-seven thousand, five hundred eighty-one".