21020201221 has 2 divisors, whose sum is σ = 21020201222. Its totient is φ = 21020201220.

The previous prime is 21020201183. The next prime is 21020201233. The reversal of 21020201221 is 12210202012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10792924321 + 10227276900 = 103889^2 + 101130^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020201221 - 2¹⁵ = 21020168453 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020201261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510100610 + 10510100611.

It is an arithmetic number, because the mean of its divisors is an integer number (10510100611).

Almost surely, 2^21020201221 is an apocalyptic number.

It is an amenable number.

21020201221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020201221 is an equidigital number, since it uses as much as digits as its factorization.

21020201221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21020201221 its reverse (12210202012), we get a palindrome (33230403233).

The spelling of 21020201221 in words is "twenty-one billion, twenty million, two hundred one thousand, two hundred twenty-one".