18973978 has 4 divisors (see below), whose sum is σ = 28460970. Its totient is φ = 9486988.

The previous prime is 18973949. The next prime is 18973979. The reversal of 18973978 is 87937981.

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., 18122049 + 851929 = 4257^2 + 923^2 .

It is a super-2 number, since 2×18973978² = 720023682288968, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (18973979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4743493 + ... + 4743496.

Almost surely, 2^18973978 is an apocalyptic number.

18973978 is a deficient number, since it is larger than the sum of its proper divisors (9486992).

18973978 is an equidigital number, since it uses as much as digits as its factorization.

18973978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9486991.

The product of its digits is 762048, while the sum is 52.

The square root of 18973978 is about 4355.9129927031. The cubic root of 18973978 is about 266.7182896586.

The spelling of 18973978 in words is "eighteen million, nine hundred seventy-three thousand, nine hundred seventy-eight".