221021221 has 2 divisors, whose sum is σ = 221021222. Its totient is φ = 221021220.

The previous prime is 221021197. The next prime is 221021249. The reversal of 221021221 is 122120122.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 139570596 + 81450625 = 11814^2 + 9025^2 .

It is a cyclic number.

It is not a de Polignac number, because 221021221 - 2¹¹ = 221019173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221021261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110510610 + 110510611.

It is an arithmetic number, because the mean of its divisors is an integer number (110510611).

Almost surely, 2^221021221 is an apocalyptic number.

It is an amenable number.

221021221 is a deficient number, since it is larger than the sum of its proper divisors (1).

221021221 is an equidigital number, since it uses as much as digits as its factorization.

221021221 is an odious number, because the sum of its binary digits is odd.

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

The square root of 221021221 is about 14866.7824696536. The cubic root of 221021221 is about 604.6137105609.

Adding to 221021221 its reverse (122120122), we get a palindrome (343141343).

The spelling of 221021221 in words is "two hundred twenty-one million, twenty-one thousand, two hundred twenty-one".