18191897 has 2 divisors, whose sum is σ = 18191898. Its totient is φ = 18191896.

The previous prime is 18191893. The next prime is 18191909. The reversal of 18191897 is 79819181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18181696 + 10201 = 4264^2 + 101^2 .

It is a cyclic number.

It is not a de Polignac number, because 18191897 - 2² = 18191893 is a prime.

It is not a weakly prime, because it can be changed into another prime (18191893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9095948 + 9095949.

It is an arithmetic number, because the mean of its divisors is an integer number (9095949).

Almost surely, 2^18191897 is an apocalyptic number.

It is an amenable number.

18191897 is a deficient number, since it is larger than the sum of its proper divisors (1).

18191897 is an equidigital number, since it uses as much as digits as its factorization.

18191897 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 44.

The square root of 18191897 is about 4265.1960095639. The cubic root of 18191897 is about 263.0021685837.

The spelling of 18191897 in words is "eighteen million, one hundred ninety-one thousand, eight hundred ninety-seven".