1221100121 has 2 divisors, whose sum is σ = 1221100122. Its totient is φ = 1221100120.

The previous prime is 1221100063. The next prime is 1221100141. The reversal of 1221100121 is 1210011221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 943411225 + 277688896 = 30715^2 + 16664^2 .

It is an emirp because it is prime and its reverse (1210011221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221100121 - 2¹⁰ = 1221099097 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221100141) 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, 610550060 + 610550061.

It is an arithmetic number, because the mean of its divisors is an integer number (610550061).

Almost surely, 2^1221100121 is an apocalyptic number.

It is an amenable number.

1221100121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221100121 is an equidigital number, since it uses as much as digits as its factorization.

1221100121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8, while the sum is 11.

The square root of 1221100121 is about 34944.2430308628. The cubic root of 1221100121 is about 1068.8508117984.

Adding to 1221100121 its reverse (1210011221), we get a palindrome (2431111342).

Subtracting from 1221100121 its reverse (1210011221), we obtain a square (11088900 = 3330²).

It can be divided in two parts, 1221100 and 121, that added together give a palindrome (1221221).

The spelling of 1221100121 in words is "one billion, two hundred twenty-one million, one hundred thousand, one hundred twenty-one".