221028221 has 2 divisors, whose sum is σ = 221028222. Its totient is φ = 221028220.

The previous prime is 221028173. The next prime is 221028257. The reversal of 221028221 is 122820122.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151905625 + 69122596 = 12325^2 + 8314^2 .

It is a cyclic number.

It is not a de Polignac number, because 221028221 - 2²⁶ = 153919357 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 221028193 and 221028202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221021221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110514110 + 110514111.

It is an arithmetic number, because the mean of its divisors is an integer number (110514111).

Almost surely, 2^221028221 is an apocalyptic number.

It is an amenable number.

221028221 is a deficient number, since it is larger than the sum of its proper divisors (1).

221028221 is an equidigital number, since it uses as much as digits as its factorization.

221028221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 221028221 is about 14867.0178919648. The cubic root of 221028221 is about 604.6200934341.

Adding to 221028221 its reverse (122820122), we get a palindrome (343848343).

The spelling of 221028221 in words is "two hundred twenty-one million, twenty-eight thousand, two hundred twenty-one".