81517131 has 8 divisors (see below), whose sum is σ = 120766160. Its totient is φ = 54344736.

The previous prime is 81517097. The next prime is 81517141. The reversal of 81517131 is 13171518.

It is not a de Polignac number, because 81517131 - 2⁷ = 81517003 is a prime.

It is a super-2 number, since 2×81517131² = 13290085292942322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 3019153 = 81517131 / (8 + 1 + 5 + 1 + 7 + 1 + 3 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81517095 and 81517104.

It is not an unprimeable number, because it can be changed into a prime (81517141) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1509550 + ... + 1509603.

It is an arithmetic number, because the mean of its divisors is an integer number (15095770).

Almost surely, 2^81517131 is an apocalyptic number.

81517131 is a deficient number, since it is larger than the sum of its proper divisors (39249029).

81517131 is a wasteful number, since it uses less digits than its factorization.

81517131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3019162 (or 3019156 counting only the distinct ones).

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

The square root of 81517131 is about 9028.6837911182. The cubic root of 81517131 is about 433.5936986910.

Adding to 81517131 its reverse (13171518), we get a palindrome (94688649).

The spelling of 81517131 in words is "eighty-one million, five hundred seventeen thousand, one hundred thirty-one".