18387220 has 24 divisors (see below), whose sum is σ = 38694600. Its totient is φ = 7339392.

The previous prime is 18387211. The next prime is 18387221. The reversal of 18387220 is 2278381.

It can be written as a sum of positive squares in 4 ways, for example, as 17424 + 18369796 = 132^2 + 4286^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18387221) 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, 16026 + ... + 17134.

It is an arithmetic number, because the mean of its divisors is an integer number (1612275).

Almost surely, 2^18387220 is an apocalyptic number.

18387220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18387220 is an abundant number, since it is smaller than the sum of its proper divisors (20307380).

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

18387220 is a wasteful number, since it uses less digits than its factorization.

18387220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1947 (or 1945 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 31.

The square root of 18387220 is about 4288.0321827151. The cubic root of 18387220 is about 263.9400881800.

The spelling of 18387220 in words is "eighteen million, three hundred eighty-seven thousand, two hundred twenty".