18909778 has 8 divisors (see below), whose sum is σ = 28384380. Its totient is φ = 9448320.

The previous prime is 18909773. The next prime is 18909791. The reversal of 18909778 is 87790981.

It can be written as a sum of positive squares in 2 ways, for example, as 18258529 + 651249 = 4273^2 + 807^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (18909773) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2038 + ... + 6478.

Almost surely, 2^18909778 is an apocalyptic number.

18909778 is a deficient number, since it is larger than the sum of its proper divisors (9474602).

18909778 is a wasteful number, since it uses less digits than its factorization.

18909778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6572.

The product of its (nonzero) digits is 254016, while the sum is 49.

The square root of 18909778 is about 4348.5374552831. The cubic root of 18909778 is about 266.4171287162.

The spelling of 18909778 in words is "eighteen million, nine hundred nine thousand, seven hundred seventy-eight".