1221210121 has 2 divisors, whose sum is σ = 1221210122. Its totient is φ = 1221210120.

The previous prime is 1221210119. The next prime is 1221210131. The reversal of 1221210121 is 1210121221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 780420096 + 440790025 = 27936^2 + 20995^2 .

It is an emirp because it is prime and its reverse (1210121221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221210121 - 2¹ = 1221210119 is a prime.

Together with 1221210119, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1221210131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610605060 + 610605061.

It is an arithmetic number, because the mean of its divisors is an integer number (610605061).

Almost surely, 2^1221210121 is an apocalyptic number.

It is an amenable number.

1221210121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221210121 is an equidigital number, since it uses as much as digits as its factorization.

1221210121 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 1221210121 is about 34945.8169313582. The cubic root of 1221210121 is about 1068.8829058250.

Adding to 1221210121 its reverse (1210121221), we get a palindrome (2431331342).

Subtracting from 1221210121 its reverse (1210121221), we obtain a square (11088900 = 3330²).

The spelling of 1221210121 in words is "one billion, two hundred twenty-one million, two hundred ten thousand, one hundred twenty-one".