18220978 has 4 divisors (see below), whose sum is σ = 27331470. Its totient is φ = 9110488.

The previous prime is 18220973. The next prime is 18220987. The reversal of 18220978 is 87902281.

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., 18207289 + 13689 = 4267^2 + 117^2 .

It is not an unprimeable number, because it can be changed into a prime (18220973) 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, 4555243 + ... + 4555246.

Almost surely, 2^18220978 is an apocalyptic number.

18220978 is a deficient number, since it is larger than the sum of its proper divisors (9110492).

18220978 is an equidigital number, since it uses as much as digits as its factorization.

18220978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9110491.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 18220978 is about 4268.6037529853. The cubic root of 18220978 is about 263.1422363329.

The spelling of 18220978 in words is "eighteen million, two hundred twenty thousand, nine hundred seventy-eight".