18209920 has 64 divisors (see below), whose sum is σ = 44767800. Its totient is φ = 7077888.

The previous prime is 18209909. The next prime is 18209921. The reversal of 18209920 is 2990281.

It can be written as a sum of positive squares in 4 ways, for example, as 16711744 + 1498176 = 4088^2 + 1224^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (18209921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23296 + ... + 24064.

Almost surely, 2^18209920 is an apocalyptic number.

18209920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18209920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22383900).

18209920 is an abundant number, since it is smaller than the sum of its proper divisors (26557880).

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

18209920 is an equidigital number, since it uses as much as digits as its factorization.

18209920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 825 (or 813 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 18209920 is about 4267.3082850903. The cubic root of 18209920 is about 263.0889933860.

The spelling of 18209920 in words is "eighteen million, two hundred nine thousand, nine hundred twenty".