15811582081 has 4 divisors (see below), whose sum is σ = 15813412164. Its totient is φ = 15809752000.

The previous prime is 15811582057. The next prime is 15811582091. The reversal of 15811582081 is 18028511851.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18028511851 = 7 ⋅2575501693.

It can be written as a sum of positive squares in 2 ways, for example, as 14873997681 + 937584400 = 121959^2 + 30620^2 .

It is a cyclic number.

It is not a de Polignac number, because 15811582081 - 2⁵ = 15811582049 is a prime.

It is a super-2 number, since 2×15811582081² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15811582021) 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, 902020 + ... + 919381.

It is an arithmetic number, because the mean of its divisors is an integer number (3953353041).

Almost surely, 2^15811582081 is an apocalyptic number.

It is an amenable number.

15811582081 is a deficient number, since it is larger than the sum of its proper divisors (1830083).

15811582081 is an equidigital number, since it uses as much as digits as its factorization.

15811582081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1830082.

The product of its (nonzero) digits is 25600, while the sum is 40.

The spelling of 15811582081 in words is "fifteen billion, eight hundred eleven million, five hundred eighty-two thousand, eighty-one".