18221280 has 384 divisors, whose sum is σ = 78382080. Its totient is φ = 3440640.

The previous prime is 18221257. The next prime is 18221339. The reversal of 18221280 is 8212281.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 18221280.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 628306 + ... + 628334.

It is an arithmetic number, because the mean of its divisors is an integer number (204120).

Almost surely, 2^18221280 is an apocalyptic number.

18221280 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 18221280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39191040).

18221280 is an abundant number, since it is smaller than the sum of its proper divisors (60160800).

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

18221280 is a wasteful number, since it uses less digits than its factorization.

18221280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82 (or 74 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 24.

The square root of 18221280 is about 4268.6391274035. The cubic root of 18221280 is about 263.1436901245.

The spelling of 18221280 in words is "eighteen million, two hundred twenty-one thousand, two hundred eighty".