11581506721 has 16 divisors (see below), whose sum is σ = 12255252480. Its totient is φ = 10929980160.

The previous prime is 11581506707. The next prime is 11581506737. The reversal of 11581506721 is 12760518511.

It is a cyclic number.

It is not a de Polignac number, because 11581506721 - 2⁵ = 11581506689 is a prime.

It is a super-3 number, since 3×11581506721³ (a number of 31 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11581506701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 172656 + ... + 230158.

It is an arithmetic number, because the mean of its divisors is an integer number (765953280).

Almost surely, 2^11581506721 is an apocalyptic number.

It is an amenable number.

11581506721 is a deficient number, since it is larger than the sum of its proper divisors (673745759).

11581506721 is an equidigital number, since it uses as much as digits as its factorization.

11581506721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57696.

The product of its (nonzero) digits is 16800, while the sum is 37.

The spelling of 11581506721 in words is "eleven billion, five hundred eighty-one million, five hundred six thousand, seven hundred twenty-one".