11861581 has 2 divisors, whose sum is σ = 11861582. Its totient is φ = 11861580.

The previous prime is 11861579. The next prime is 11861599. The reversal of 11861581 is 18516811.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10989225 + 872356 = 3315^2 + 934^2 .

It is a cyclic number.

It is not a de Polignac number, because 11861581 - 2¹ = 11861579 is a prime.

It is a super-2 number, since 2×11861581² = 281394207639122, which contains 22 as substring.

Together with 11861579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11861081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5930790 + 5930791.

It is an arithmetic number, because the mean of its divisors is an integer number (5930791).

Almost surely, 2^11861581 is an apocalyptic number.

It is an amenable number.

11861581 is a deficient number, since it is larger than the sum of its proper divisors (1).

11861581 is an equidigital number, since it uses as much as digits as its factorization.

11861581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 31.

The square root of 11861581 is about 3444.0646045044. The cubic root of 11861581 is about 228.0591631118.

The spelling of 11861581 in words is "eleven million, eight hundred sixty-one thousand, five hundred eighty-one".