21020212121 has 2 divisors, whose sum is σ = 21020212122. Its totient is φ = 21020212120.

The previous prime is 21020212111. The next prime is 21020212159. The reversal of 21020212121 is 12121202012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16322617600 + 4697594521 = 127760^2 + 68539^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020212121 is a prime.

It is a super-2 number, since 2×21020212121² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21020212096 and 21020212105.

It is not a weakly prime, because it can be changed into another prime (21020212111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510106060 + 10510106061.

It is an arithmetic number, because the mean of its divisors is an integer number (10510106061).

Almost surely, 2^21020212121 is an apocalyptic number.

It is an amenable number.

21020212121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020212121 is an equidigital number, since it uses as much as digits as its factorization.

21020212121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21020212121 its reverse (12121202012), we get a palindrome (33141414133).

The spelling of 21020212121 in words is "twenty-one billion, twenty million, two hundred twelve thousand, one hundred twenty-one".