81131515 has 8 divisors (see below), whose sum is σ = 97418448. Its totient is φ = 64864800.

The previous prime is 81131509. The next prime is 81131551. The reversal of 81131515 is 51513118.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81131515 - 2¹¹ = 81129467 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81131515.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5965 + ... + 14065.

It is an arithmetic number, because the mean of its divisors is an integer number (12177306).

Almost surely, 2^81131515 is an apocalyptic number.

81131515 is a deficient number, since it is larger than the sum of its proper divisors (16286933).

81131515 is a wasteful number, since it uses less digits than its factorization.

81131515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10109.

The product of its digits is 600, while the sum is 25.

The square root of 81131515 is about 9007.3034255542. The cubic root of 81131515 is about 432.9089141646.

The spelling of 81131515 in words is "eighty-one million, one hundred thirty-one thousand, five hundred fifteen".