81991822 has 16 divisors (see below), whose sum is σ = 134348544. Its totient is φ = 37219000.

The previous prime is 81991817. The next prime is 81991831. The reversal of 81991822 is 22819918.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17997 + ... + 22087.

It is an arithmetic number, because the mean of its divisors is an integer number (8396784).

Almost surely, 2^81991822 is an apocalyptic number.

81991822 is a deficient number, since it is larger than the sum of its proper divisors (52356722).

81991822 is a wasteful number, since it uses less digits than its factorization.

81991822 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5015.

The product of its digits is 20736, while the sum is 40.

The square root of 81991822 is about 9054.9335723682. The cubic root of 81991822 is about 434.4337053448.

The spelling of 81991822 in words is "eighty-one million, nine hundred ninety-one thousand, eight hundred twenty-two".