81991827 has 6 divisors (see below), whose sum is σ = 118432652. Its totient is φ = 54661212.

The previous prime is 81991817. The next prime is 81991831. The reversal of 81991827 is 72819918.

It is not a de Polignac number, because 81991827 - 2¹⁶ = 81926291 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81991817) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4555093 + ... + 4555110.

Almost surely, 2^81991827 is an apocalyptic number.

81991827 is a deficient number, since it is larger than the sum of its proper divisors (36440825).

81991827 is a wasteful number, since it uses less digits than its factorization.

81991827 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9110209 (or 9110206 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 81991827 is about 9054.9338484607. The cubic root of 81991827 is about 434.4337141757.

The spelling of 81991827 in words is "eighty-one million, nine hundred ninety-one thousand, eight hundred twenty-seven".