21002221421 has 2 divisors, whose sum is σ = 21002221422. Its totient is φ = 21002221420.

The previous prime is 21002221411. The next prime is 21002221433. The reversal of 21002221421 is 12412220012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13319698921 + 7682522500 = 115411^2 + 87650^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002221421 - 2¹⁰ = 21002220397 is a prime.

It is a super-2 number, since 2×21002221421² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21002221421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21002221411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501110710 + 10501110711.

It is an arithmetic number, because the mean of its divisors is an integer number (10501110711).

Almost surely, 2^21002221421 is an apocalyptic number.

It is an amenable number.

21002221421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002221421 is an equidigital number, since it uses as much as digits as its factorization.

21002221421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21002221421 its reverse (12412220012), we get a palindrome (33414441433).

The spelling of 21002221421 in words is "twenty-one billion, two million, two hundred twenty-one thousand, four hundred twenty-one".