18649978 has 4 divisors (see below), whose sum is σ = 27974970. Its totient is φ = 9324988.

The previous prime is 18649973. The next prime is 18649979. The reversal of 18649978 is 87994681.

It is a happy number.

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., 14311089 + 4338889 = 3783^2 + 2083^2 .

It is not an unprimeable number, because it can be changed into a prime (18649973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4662493 + ... + 4662496.

Almost surely, 2^18649978 is an apocalyptic number.

18649978 is a deficient number, since it is larger than the sum of its proper divisors (9324992).

18649978 is an equidigital number, since it uses as much as digits as its factorization.

18649978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9324991.

The product of its digits is 870912, while the sum is 52.

The square root of 18649978 is about 4318.5620291944. The cubic root of 18649978 is about 265.1914031946.

The spelling of 18649978 in words is "eighteen million, six hundred forty-nine thousand, nine hundred seventy-eight".