11855791581 has 4 divisors (see below), whose sum is σ = 15807722112. Its totient is φ = 7903861052.

The previous prime is 11855791543. The next prime is 11855791603. The reversal of 11855791581 is 18519755811.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 11855791581 - 2¹⁹ = 11855267293 is a prime.

It is a super-2 number, since 2×11855791581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11855791511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1975965261 + ... + 1975965266.

It is an arithmetic number, because the mean of its divisors is an integer number (3951930528).

Almost surely, 2^11855791581 is an apocalyptic number.

It is an amenable number.

11855791581 is a deficient number, since it is larger than the sum of its proper divisors (3951930531).

11855791581 is an equidigital number, since it uses as much as digits as its factorization.

11855791581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3951930530.

The product of its digits is 504000, while the sum is 51.

The spelling of 11855791581 in words is "eleven billion, eight hundred fifty-five million, seven hundred ninety-one thousand, five hundred eighty-one".