21202122121 has 2 divisors, whose sum is σ = 21202122122. Its totient is φ = 21202122120.

The previous prime is 21202122119. The next prime is 21202122143. The reversal of 21202122121 is 12122120212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18140049225 + 3062072896 = 134685^2 + 55336^2 .

It is a cyclic number.

It is not a de Polignac number, because 21202122121 - 2¹ = 21202122119 is a prime.

Together with 21202122119, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21202122095 and 21202122104.

It is not a weakly prime, because it can be changed into another prime (21202122181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601061060 + 10601061061.

It is an arithmetic number, because the mean of its divisors is an integer number (10601061061).

Almost surely, 2^21202122121 is an apocalyptic number.

It is an amenable number.

21202122121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21202122121 is an equidigital number, since it uses as much as digits as its factorization.

21202122121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21202122121 its reverse (12122120212), we get a palindrome (33324242333).

The spelling of 21202122121 in words is "twenty-one billion, two hundred two million, one hundred twenty-two thousand, one hundred twenty-one".