81578131 has 4 divisors (see below), whose sum is σ = 84391200. Its totient is φ = 78765064.

The previous prime is 81578111. The next prime is 81578141. The reversal of 81578131 is 13187518.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81578131 is a prime.

It is a super-2 number, since 2×81578131² = 13309982914906322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81578111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1406491 + ... + 1406548.

It is an arithmetic number, because the mean of its divisors is an integer number (21097800).

Almost surely, 2^81578131 is an apocalyptic number.

81578131 is a deficient number, since it is larger than the sum of its proper divisors (2813069).

81578131 is a wasteful number, since it uses less digits than its factorization.

81578131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2813068.

The product of its digits is 6720, while the sum is 34.

The square root of 81578131 is about 9032.0612819002. The cubic root of 81578131 is about 433.7018257421.

The spelling of 81578131 in words is "eighty-one million, five hundred seventy-eight thousand, one hundred thirty-one".