11991173081 has 2 divisors, whose sum is σ = 11991173082. Its totient is φ = 11991173080.

The previous prime is 11991173063. The next prime is 11991173179. The reversal of 11991173081 is 18037119911.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10441569856 + 1549603225 = 102184^2 + 39365^2 .

It is a cyclic number.

It is not a de Polignac number, because 11991173081 - 2¹⁰ = 11991172057 is a prime.

It is a super-2 number, since 2×11991173081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (11991173981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5995586540 + 5995586541.

It is an arithmetic number, because the mean of its divisors is an integer number (5995586541).

Almost surely, 2^11991173081 is an apocalyptic number.

It is an amenable number.

11991173081 is a deficient number, since it is larger than the sum of its proper divisors (1).

11991173081 is an equidigital number, since it uses as much as digits as its factorization.

11991173081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13608, while the sum is 41.

The spelling of 11991173081 in words is "eleven billion, nine hundred ninety-one million, one hundred seventy-three thousand, eighty-one".