81799591 has 4 divisors (see below), whose sum is σ = 82000000. Its totient is φ = 81599184.

The previous prime is 81799567. The next prime is 81799621. The reversal of 81799591 is 19599718.

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 81799591 - 2⁷ = 81799463 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 (81799561) 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, 99591 + ... + 100408.

It is an arithmetic number, because the mean of its divisors is an integer number (20500000).

Almost surely, 2^81799591 is an apocalyptic number.

81799591 is a deficient number, since it is larger than the sum of its proper divisors (200409).

81799591 is a wasteful number, since it uses less digits than its factorization.

81799591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 200408.

The product of its digits is 204120, while the sum is 49.

The square root of 81799591 is about 9044.3126328096. The cubic root of 81799591 is about 434.0939276554.

The spelling of 81799591 in words is "eighty-one million, seven hundred ninety-nine thousand, five hundred ninety-one".