21331212121 has 2 divisors, whose sum is σ = 21331212122. Its totient is φ = 21331212120.

The previous prime is 21331212113. The next prime is 21331212173. The reversal of 21331212121 is 12121213312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13372609600 + 7958602521 = 115640^2 + 89211^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331212121 - 2³ = 21331212113 is a prime.

It is a super-2 number, since 2×21331212121² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21331218121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665606060 + 10665606061.

It is an arithmetic number, because the mean of its divisors is an integer number (10665606061).

Almost surely, 2^21331212121 is an apocalyptic number.

It is an amenable number.

21331212121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331212121 is an equidigital number, since it uses as much as digits as its factorization.

21331212121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 144, while the sum is 19.

Adding to 21331212121 its reverse (12121213312), we get a palindrome (33452425433).

The spelling of 21331212121 in words is "twenty-one billion, three hundred thirty-one million, two hundred twelve thousand, one hundred twenty-one".