221220221 has 4 divisors (see below), whose sum is σ = 224846844. Its totient is φ = 217593600.

The previous prime is 221220163. The next prime is 221220229. The reversal of 221220221 is 122022122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 122022122 = 2 ⋅61011061.

It can be written as a sum of positive squares in 2 ways, for example, as 67732900 + 153487321 = 8230^2 + 12389^2 .

It is a cyclic number.

It is not a de Polignac number, because 221220221 - 2¹⁸ = 220958077 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221220196 and 221220205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221220229) 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, 1813220 + ... + 1813341.

It is an arithmetic number, because the mean of its divisors is an integer number (56211711).

Almost surely, 2^221220221 is an apocalyptic number.

It is an amenable number.

221220221 is a deficient number, since it is larger than the sum of its proper divisors (3626623).

221220221 is an equidigital number, since it uses as much as digits as its factorization.

221220221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3626622.

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 221220221 is about 14873.4737368242. The cubic root of 221220221 is about 604.7951140114.

Adding to 221220221 its reverse (122022122), we get a palindrome (343242343).

It can be divided in two parts, 22 and 1220221, that multiplied together give a palindrome (26844862).

The spelling of 221220221 in words is "two hundred twenty-one million, two hundred twenty thousand, two hundred twenty-one".