221520618 has 96 divisors (see below), whose sum is σ = 547223040. Its totient is φ = 64149120.

The previous prime is 221520577. The next prime is 221520619. The reversal of 221520618 is 816025122.

It is a happy number.

221520618 is a `hidden beast` number, since 2 + 21 + 5 + 20 + 618 = 666.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 221520591 and 221520600.

It is not an unprimeable number, because it can be changed into a prime (221520619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 993255 + ... + 993477.

It is an arithmetic number, because the mean of its divisors is an integer number (5700240).

Almost surely, 2^221520618 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221520618, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (273611520).

221520618 is an abundant number, since it is smaller than the sum of its proper divisors (325702422).

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

221520618 is a wasteful number, since it uses less digits than its factorization.

221520618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444 (or 441 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 221520618 is about 14883.5687252755. The cubic root of 221520618 is about 605.0687425020.

The spelling of 221520618 in words is "two hundred twenty-one million, five hundred twenty thousand, six hundred eighteen".