81516139 has 4 divisors (see below), whose sum is σ = 86311224. Its totient is φ = 76721056.

The previous prime is 81516121. The next prime is 81516151. The reversal of 81516139 is 93161518.

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

It is a cyclic number.

It is not a de Polignac number, because 81516139 - 2⁷ = 81516011 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81516109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2397517 + ... + 2397550.

It is an arithmetic number, because the mean of its divisors is an integer number (21577806).

Almost surely, 2^81516139 is an apocalyptic number.

81516139 is a deficient number, since it is larger than the sum of its proper divisors (4795085).

81516139 is a wasteful number, since it uses less digits than its factorization.

81516139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4795084.

The product of its digits is 6480, while the sum is 34.

The square root of 81516139 is about 9028.6288549259. The cubic root of 81516139 is about 433.5919398513.

The spelling of 81516139 in words is "eighty-one million, five hundred sixteen thousand, one hundred thirty-nine".