221521221 has 12 divisors (see below), whose sum is σ = 320928972. Its totient is φ = 147240576.

The previous prime is 221521217. The next prime is 221521241. The reversal of 221521221 is 122125122.

It can be written as a sum of positive squares in 2 ways, for example, as 149084100 + 72437121 = 12210^2 + 8511^2 .

It is not a de Polignac number, because 221521221 - 2² = 221521217 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 221521194 and 221521203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221521241) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 33486 + ... + 39551.

It is an arithmetic number, because the mean of its divisors is an integer number (26744081).

Almost surely, 2^221521221 is an apocalyptic number.

It is an amenable number.

221521221 is a deficient number, since it is larger than the sum of its proper divisors (99407751).

221521221 is a wasteful number, since it uses less digits than its factorization.

221521221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73380 (or 73377 counting only the distinct ones).

The product of its digits is 160, while the sum is 18.

The square root of 221521221 is about 14883.5889825002. The cubic root of 221521221 is about 605.0692915195.

Adding to 221521221 its reverse (122125122), we get a palindrome (343646343).

It can be divided in two parts, 2215 and 21221, that added together give a triangular number (23436 = T₂₁₆).

The spelling of 221521221 in words is "two hundred twenty-one million, five hundred twenty-one thousand, two hundred twenty-one".