21230312221 has 2 divisors, whose sum is σ = 21230312222. Its totient is φ = 21230312220.

The previous prime is 21230312209. The next prime is 21230312227. The reversal of 21230312221 is 12221303212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16659064900 + 4571247321 = 129070^2 + 67611^2 .

It is a cyclic number.

It is not a de Polignac number, because 21230312221 - 2²¹ = 21228215069 is a prime.

It is a super-2 number, since 2×21230312221² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21230312227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615156110 + 10615156111.

It is an arithmetic number, because the mean of its divisors is an integer number (10615156111).

Almost surely, 2^21230312221 is an apocalyptic number.

It is an amenable number.

21230312221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21230312221 is an equidigital number, since it uses as much as digits as its factorization.

21230312221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21230312221 its reverse (12221303212), we get a palindrome (33451615433).

Subtracting from 21230312221 its reverse (12221303212), we obtain a palindrome (9009009009).

The spelling of 21230312221 in words is "twenty-one billion, two hundred thirty million, three hundred twelve thousand, two hundred twenty-one".