81136791 has 6 divisors (see below), whose sum is σ = 117197600. Its totient is φ = 54091188.

The previous prime is 81136789. The next prime is 81136793. The reversal of 81136791 is 19763118.

It is an interprime number because it is at equal distance from previous prime (81136789) and next prime (81136793).

It is not a de Polignac number, because 81136791 - 2¹ = 81136789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81136793) 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 5 ways as a sum of consecutive naturals, for example, 4507591 + ... + 4507608.

Almost surely, 2^81136791 is an apocalyptic number.

81136791 is a deficient number, since it is larger than the sum of its proper divisors (36060809).

81136791 is a wasteful number, since it uses less digits than its factorization.

81136791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9015205 (or 9015202 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 81136791 is about 9007.5962942397. The cubic root of 81136791 is about 432.9182980147.

The spelling of 81136791 in words is "eighty-one million, one hundred thirty-six thousand, seven hundred ninety-one".