221525221 has 4 divisors (see below), whose sum is σ = 225156844. Its totient is φ = 217893600.

The previous prime is 221525191. The next prime is 221525233. The reversal of 221525221 is 122525122.

221525221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10956100 + 210569121 = 3310^2 + 14511^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221525221 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221525192 and 221525201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221525261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1815720 + ... + 1815841.

It is an arithmetic number, because the mean of its divisors is an integer number (56289211).

Almost surely, 2^221525221 is an apocalyptic number.

It is an amenable number.

221525221 is a deficient number, since it is larger than the sum of its proper divisors (3631623).

221525221 is an equidigital number, since it uses as much as digits as its factorization.

221525221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3631622.

The product of its digits is 800, while the sum is 22.

The square root of 221525221 is about 14883.7233580848. The cubic root of 221525221 is about 605.0729334017.

Subtracting from 221525221 its reverse (122525122), we obtain a palindrome (99000099).

The spelling of 221525221 in words is "two hundred twenty-one million, five hundred twenty-five thousand, two hundred twenty-one".