18990091 has 2 divisors, whose sum is σ = 18990092. Its totient is φ = 18990090.

The previous prime is 18990079. The next prime is 18990109. The reversal of 18990091 is 19009981.

Together with next prime (18990109) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is an emirp because it is prime and its reverse (19009981) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18990091 - 2¹³ = 18981899 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18990091.

It is not a weakly prime, because it can be changed into another prime (18990061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9495045 + 9495046.

It is an arithmetic number, because the mean of its divisors is an integer number (9495046).

Almost surely, 2^18990091 is an apocalyptic number.

18990091 is a deficient number, since it is larger than the sum of its proper divisors (1).

18990091 is an equidigital number, since it uses as much as digits as its factorization.

18990091 is an odious number, because the sum of its binary digits is odd.

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

The square root of 18990091 is about 4357.7621550516. The cubic root of 18990091 is about 266.7937687496.

The spelling of 18990091 in words is "eighteen million, nine hundred ninety thousand, ninety-one".