221581872 has 40 divisors (see below), whose sum is σ = 636023280. Its totient is φ = 73860480.

The previous prime is 221581847. The next prime is 221581873. The reversal of 221581872 is 278185122.

221581872 is a `hidden beast` number, since 2 + 2 + 1 + 581 + 8 + 72 = 666.

221581872 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (221581873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 256029 + ... + 256892.

It is an arithmetic number, because the mean of its divisors is an integer number (15900582).

Almost surely, 2^221581872 is an apocalyptic number.

It is an amenable number.

221581872 is an abundant number, since it is smaller than the sum of its proper divisors (414441408).

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

221581872 is a wasteful number, since it uses less digits than its factorization.

221581872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 512938 (or 512926 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 221581872 is about 14885.6263556493. The cubic root of 221581872 is about 605.1245077628.

The spelling of 221581872 in words is "two hundred twenty-one million, five hundred eighty-one thousand, eight hundred seventy-two".