11611981 has 2 divisors, whose sum is σ = 11611982. Its totient is φ = 11611980.

The previous prime is 11611939. The next prime is 11612047. The reversal of 11611981 is 18911611.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11594025 + 17956 = 3405^2 + 134^2 .It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 18611911 and 11911681.

It is a cyclic number.

It is not a de Polignac number, because 11611981 - 2¹¹ = 11609933 is a prime.

It is a super-2 number, since 2×11611981² = 269676205488722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11611931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5805990 + 5805991.

It is an arithmetic number, because the mean of its divisors is an integer number (5805991).

Almost surely, 2^11611981 is an apocalyptic number.

It is an amenable number.

11611981 is a deficient number, since it is larger than the sum of its proper divisors (1).

11611981 is an equidigital number, since it uses as much as digits as its factorization.

11611981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 28.

The square root of 11611981 is about 3407.6356906219. The cubic root of 11611981 is about 226.4481474866.

The spelling of 11611981 in words is "eleven million, six hundred eleven thousand, nine hundred eighty-one".