18815987 has 2 divisors, whose sum is σ = 18815988. Its totient is φ = 18815986.

The previous prime is 18815941. The next prime is 18816019. The reversal of 18815987 is 78951881.

It is a strong prime.

It is an emirp because it is prime and its reverse (78951881) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18815987 - 2²⁰ = 17767411 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18815917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9407993 + 9407994.

It is an arithmetic number, because the mean of its divisors is an integer number (9407994).

Almost surely, 2^18815987 is an apocalyptic number.

18815987 is a deficient number, since it is larger than the sum of its proper divisors (1).

18815987 is an equidigital number, since it uses as much as digits as its factorization.

18815987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 161280, while the sum is 47.

The square root of 18815987 is about 4337.7398492763. The cubic root of 18815987 is about 265.9759291916.

The spelling of 18815987 in words is "eighteen million, eight hundred fifteen thousand, nine hundred eighty-seven".