221556720 has 320 divisors, whose sum is σ = 902799360. Its totient is φ = 43545600.

The previous prime is 221556719. The next prime is 221556757. The reversal of 221556720 is 27655122.

It is a Harshad number since it is a multiple of its sum of digits (30).

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, 350805 + ... + 351435.

It is an arithmetic number, because the mean of its divisors is an integer number (2821248).

Almost surely, 2^221556720 is an apocalyptic number.

221556720 is a gapful number since it is divisible by the number (20) 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 221556720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (451399680).

221556720 is an abundant number, since it is smaller than the sum of its proper divisors (681242640).

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

221556720 is a wasteful number, since it uses less digits than its factorization.

221556720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 684 (or 678 counting only the distinct ones).

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 221556720 is about 14884.7814898305. The cubic root of 221556720 is about 605.1016107821.

The spelling of 221556720 in words is "two hundred twenty-one million, five hundred fifty-six thousand, seven hundred twenty".