21202121 has 2 divisors, whose sum is σ = 21202122. Its totient is φ = 21202120.

The previous prime is 21202079. The next prime is 21202127. The reversal of 21202121 is 12120212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15912121 + 5290000 = 3989^2 + 2300^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21202121 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21202127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601060 + 10601061.

It is an arithmetic number, because the mean of its divisors is an integer number (10601061).

Almost surely, 2^21202121 is an apocalyptic number.

It is an amenable number.

21202121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21202121 is an equidigital number, since it uses as much as digits as its factorization.

21202121 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 11.

The square root of 21202121 is about 4604.5760934097. The cubic root of 21202121 is about 276.7747302895.

Adding to 21202121 its reverse (12120212), we get a palindrome (33322333).

The spelling of 21202121 in words is "twenty-one million, two hundred two thousand, one hundred twenty-one".