11721605021581 has 32 divisors (see below), whose sum is σ = 14735506867200. Its totient is φ = 9075700740096.

The previous prime is 11721605021573. The next prime is 11721605021657. The reversal of 11721605021581 is 18512050612711.

It is a cyclic number.

It is not a de Polignac number, because 11721605021581 - 2³ = 11721605021573 is a prime.

It is a super-2 number, since 2×11721605021581² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11721605001581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 32535625 + ... + 32893921.

It is an arithmetic number, because the mean of its divisors is an integer number (460484589600).

Almost surely, 2^{11721605021581} is an apocalyptic number.

It is an amenable number.

11721605021581 is a deficient number, since it is larger than the sum of its proper divisors (3013901845619).

11721605021581 is a wasteful number, since it uses less digits than its factorization.

11721605021581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 366013.

The product of its (nonzero) digits is 33600, while the sum is 40.

The spelling of 11721605021581 in words is "eleven trillion, seven hundred twenty-one billion, six hundred five million, twenty-one thousand, five hundred eighty-one".