18899978 has 4 divisors (see below), whose sum is σ = 28349970. Its totient is φ = 9449988.

The previous prime is 18899977. The next prime is 18899981. The reversal of 18899978 is 87999881.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87999881 = 61 ⋅1442621.

It can be written as a sum of positive squares in only one way, i.e., 11539609 + 7360369 = 3397^2 + 2713^2 .

It is not an unprimeable number, because it can be changed into a prime (18899977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4724993 + ... + 4724996.

Almost surely, 2^18899978 is an apocalyptic number.

18899978 is a deficient number, since it is larger than the sum of its proper divisors (9449992).

18899978 is an equidigital number, since it uses as much as digits as its factorization.

18899978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9449991.

The product of its digits is 2612736, while the sum is 59.

The square root of 18899978 is about 4347.4104936157. The cubic root of 18899978 is about 266.3710971688.

The spelling of 18899978 in words is "eighteen million, eight hundred ninety-nine thousand, nine hundred seventy-eight".