81131157 has 24 divisors (see below), whose sum is σ = 124464600. Its totient is φ = 50749440.

The previous prime is 81131147. The next prime is 81131173. The reversal of 81131157 is 75113118.

It can be written as a sum of positive squares in 4 ways, for example, as 45239076 + 35892081 = 6726^2 + 5991^2 .

It is not a de Polignac number, because 81131157 - 2⁶ = 81131093 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81131157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81131107) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 68107 + ... + 69287.

It is an arithmetic number, because the mean of its divisors is an integer number (5186025).

Almost surely, 2^81131157 is an apocalyptic number.

It is an amenable number.

81131157 is a deficient number, since it is larger than the sum of its proper divisors (43333443).

81131157 is a wasteful number, since it uses less digits than its factorization.

81131157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1653 (or 1650 counting only the distinct ones).

The product of its digits is 840, while the sum is 27.

The square root of 81131157 is about 9007.2835527699. The cubic root of 81131157 is about 432.9082774140.

The spelling of 81131157 in words is "eighty-one million, one hundred thirty-one thousand, one hundred fifty-seven".