81177491 has 4 divisors (see below), whose sum is σ = 81252192. Its totient is φ = 81102792.

The previous prime is 81177469. The next prime is 81177539. The reversal of 81177491 is 19477118.

It is a happy number.

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 81177491 - 2⁶ = 81177427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81177461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35696 + ... + 37901.

It is an arithmetic number, because the mean of its divisors is an integer number (20313048).

Almost surely, 2^81177491 is an apocalyptic number.

81177491 is a deficient number, since it is larger than the sum of its proper divisors (74701).

81177491 is a wasteful number, since it uses less digits than its factorization.

81177491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74700.

The product of its digits is 14112, while the sum is 38.

The square root of 81177491 is about 9009.8552152629. The cubic root of 81177491 is about 432.9906730297.

The spelling of 81177491 in words is "eighty-one million, one hundred seventy-seven thousand, four hundred ninety-one".