1221221 has 2 divisors, whose sum is σ = 1221222. Its totient is φ = 1221220.

The previous prime is 1221197. The next prime is 1221223.

It is a happy number.

1221221 is nontrivially palindromic in base 10.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1221025 + 196 = 1105^2 + 14^2 .

It is a palprime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221221 is a prime.

Together with 1221223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610610 + 610611.

It is an arithmetic number, because the mean of its divisors is an integer number (610611).

2^1221221 is an apocalyptic number.

It is an amenable number.

1221221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221221 is an equidigital number, since it uses as much as digits as its factorization.

1221221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16, while the sum is 11.

The square root of 1221221 is about 1105.0886842240. The cubic root of 1221221 is about 106.8886079819. Note that the first 3 decimals are identical.

Multiplying 1221221 by its sum of digits (11), we get a palindrome (13433431).

The spelling of 1221221 in words is "one million, two hundred twenty-one thousand, two hundred twenty-one".