1221101221 has 2 divisors, whose sum is σ = 1221101222. Its totient is φ = 1221101220.

The previous prime is 1221101209. The next prime is 1221101251. The reversal of 1221101221 is 1221011221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 999508225 + 221592996 = 31615^2 + 14886^2 .

It is an emirp because it is prime and its reverse (1221011221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221101221 - 2¹⁹ = 1220576933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221101251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610550610 + 610550611.

It is an arithmetic number, because the mean of its divisors is an integer number (610550611).

Almost surely, 2^1221101221 is an apocalyptic number.

It is an amenable number.

1221101221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221101221 is an equidigital number, since it uses as much as digits as its factorization.

1221101221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 1221101221 is about 34944.2587702186. The cubic root of 1221101221 is about 1068.8511327482.

Adding to 1221101221 its reverse (1221011221), we get a palindrome (2442112442).

Subtracting from 1221101221 its reverse (1221011221), we obtain a square (90000 = 300²).

The spelling of 1221101221 in words is "one billion, two hundred twenty-one million, one hundred one thousand, two hundred twenty-one".