18451220 has 12 divisors (see below), whose sum is σ = 38747604. Its totient is φ = 7380480.

The previous prime is 18451211. The next prime is 18451249. The reversal of 18451220 is 2215481.

It can be written as a sum of positive squares in 2 ways, for example, as 14273284 + 4177936 = 3778^2 + 2044^2 .

It is a congruent number.

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, 461261 + ... + 461300.

It is an arithmetic number, because the mean of its divisors is an integer number (3228967).

Almost surely, 2^18451220 is an apocalyptic number.

18451220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18451220 is an abundant number, since it is smaller than the sum of its proper divisors (20296384).

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

18451220 is a wasteful number, since it uses less digits than its factorization.

18451220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 922570 (or 922568 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 18451220 is about 4295.4883307955. The cubic root of 18451220 is about 264.2459637596.

The spelling of 18451220 in words is "eighteen million, four hundred fifty-one thousand, two hundred twenty".