18909640 has 16 divisors (see below), whose sum is σ = 42546780. Its totient is φ = 7563840.

The previous prime is 18909629. The next prime is 18909673. The reversal of 18909640 is 4690981.

It can be written as a sum of positive squares in 2 ways, for example, as 18714276 + 195364 = 4326^2 + 442^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 18909640.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 236331 + ... + 236410.

Almost surely, 2^18909640 is an apocalyptic number.

18909640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18909640 is an abundant number, since it is smaller than the sum of its proper divisors (23637140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18909640 is a wasteful number, since it uses less digits than its factorization.

18909640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 472752 (or 472748 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 18909640 is about 4348.5215878503. The cubic root of 18909640 is about 266.4164806272.

The spelling of 18909640 in words is "eighteen million, nine hundred nine thousand, six hundred forty".