81091099 has 2 divisors, whose sum is σ = 81091100. Its totient is φ = 81091098.

The previous prime is 81091097. The next prime is 81091141. The reversal of 81091099 is 99019018.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81091099 - 2¹ = 81091097 is a prime.

Together with 81091097, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81091093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40545549 + 40545550.

It is an arithmetic number, because the mean of its divisors is an integer number (40545550).

Almost surely, 2^81091099 is an apocalyptic number.

81091099 is a deficient number, since it is larger than the sum of its proper divisors (1).

81091099 is an equidigital number, since it uses as much as digits as its factorization.

81091099 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 37.

The square root of 81091099 is about 9005.0596333395. The cubic root of 81091099 is about 432.8370171022.

The spelling of 81091099 in words is "eighty-one million, ninety-one thousand, ninety-nine".