18871999 has 2 divisors, whose sum is σ = 18872000. Its totient is φ = 18871998.

The previous prime is 18871981. The next prime is 18872003. The reversal of 18871999 is 99917881.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18871999 - 2⁵ = 18871967 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18871499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9435999 + 9436000.

It is an arithmetic number, because the mean of its divisors is an integer number (9436000).

Almost surely, 2^18871999 is an apocalyptic number.

18871999 is a deficient number, since it is larger than the sum of its proper divisors (1).

18871999 is an equidigital number, since it uses as much as digits as its factorization.

18871999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 52.

The square root of 18871999 is about 4344.1914092268. The cubic root of 18871999 is about 266.2395894744.

The spelling of 18871999 in words is "eighteen million, eight hundred seventy-one thousand, nine hundred ninety-nine".