21420212221 has 2 divisors, whose sum is σ = 21420212222. Its totient is φ = 21420212220.

The previous prime is 21420212183. The next prime is 21420212237. The reversal of 21420212221 is 12221202412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21407786596 + 12425625 = 146314^2 + 3525^2 .

It is a cyclic number.

It is not a de Polignac number, because 21420212221 - 2²³ = 21411823613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21420212291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710106110 + 10710106111.

It is an arithmetic number, because the mean of its divisors is an integer number (10710106111).

Almost surely, 2^21420212221 is an apocalyptic number.

It is an amenable number.

21420212221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420212221 is an equidigital number, since it uses as much as digits as its factorization.

21420212221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 256, while the sum is 19.

Adding to 21420212221 its reverse (12221202412), we get a palindrome (33641414633).

The spelling of 21420212221 in words is "twenty-one billion, four hundred twenty million, two hundred twelve thousand, two hundred twenty-one".