81799191 has 12 divisors (see below), whose sum is σ = 118471080. Its totient is φ = 54386640.

The previous prime is 81799187. The next prime is 81799213. The reversal of 81799191 is 19199718.

It is not a de Polignac number, because 81799191 - 2² = 81799187 is a prime.

It is a super-2 number, since 2×81799191² = 13382215296508962, which contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81799181) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8580 + ... + 15401.

It is an arithmetic number, because the mean of its divisors is an integer number (9872590).

Almost surely, 2^81799191 is an apocalyptic number.

81799191 is a deficient number, since it is larger than the sum of its proper divisors (36671889).

81799191 is a wasteful number, since it uses less digits than its factorization.

81799191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24366 (or 24363 counting only the distinct ones).

The product of its digits is 40824, while the sum is 45.

The square root of 81799191 is about 9044.2905194382. The cubic root of 81799191 is about 434.0932200812.

The spelling of 81799191 in words is "eighty-one million, seven hundred ninety-nine thousand, one hundred ninety-one".