18987818 has 4 divisors (see below), whose sum is σ = 28481730. Its totient is φ = 9493908.

The previous prime is 18987803. The next prime is 18987853. The reversal of 18987818 is 81878981.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 17530969 + 1456849 = 4187^2 + 1207^2 .

It is a super-2 number, since 2×18987818² = 721074464802248, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4746953 + ... + 4746956.

Almost surely, 2^18987818 is an apocalyptic number.

18987818 is a deficient number, since it is larger than the sum of its proper divisors (9493912).

18987818 is an equidigital number, since it uses as much as digits as its factorization.

18987818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9493911.

The product of its digits is 258048, while the sum is 50.

The square root of 18987818 is about 4357.5013482499. The cubic root of 18987818 is about 266.7831237869.

The spelling of 18987818 in words is "eighteen million, nine hundred eighty-seven thousand, eight hundred eighteen".