220121221 has 4 divisors (see below), whose sum is σ = 221393772. Its totient is φ = 218848672.

The previous prime is 220121203. The next prime is 220121233. The reversal of 220121221 is 122121022.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 122121022 = 2 ⋅61060511.

It can be written as a sum of positive squares in 2 ways, for example, as 80550625 + 139570596 = 8975^2 + 11814^2 .

It is a cyclic number.

It is not a de Polignac number, because 220121221 - 2⁵ = 220121189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (220121021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 636016 + ... + 636361.

It is an arithmetic number, because the mean of its divisors is an integer number (55348443).

Almost surely, 2^220121221 is an apocalyptic number.

It is an amenable number.

220121221 is a deficient number, since it is larger than the sum of its proper divisors (1272551).

220121221 is a wasteful number, since it uses less digits than its factorization.

220121221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1272550.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 220121221 is about 14836.4827705221. The cubic root of 220121221 is about 603.7919303266.

Adding to 220121221 its reverse (122121022), we get a palindrome (342242243).

The spelling of 220121221 in words is "two hundred twenty million, one hundred twenty-one thousand, two hundred twenty-one".