18937978 has 4 divisors (see below), whose sum is σ = 28406970. Its totient is φ = 9468988.

The previous prime is 18937973. The next prime is 18937979. The reversal of 18937978 is 87973981.

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., 11002489 + 7935489 = 3317^2 + 2817^2 .

It is not an unprimeable number, because it can be changed into a prime (18937973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4734493 + ... + 4734496.

Almost surely, 2^18937978 is an apocalyptic number.

18937978 is a deficient number, since it is larger than the sum of its proper divisors (9468992).

18937978 is an equidigital number, since it uses as much as digits as its factorization.

18937978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9468991.

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

The square root of 18937978 is about 4351.7787168008. The cubic root of 18937978 is about 266.5494981786.

The spelling of 18937978 in words is "eighteen million, nine hundred thirty-seven thousand, nine hundred seventy-eight".