21011202221 has 2 divisors, whose sum is σ = 21011202222. Its totient is φ = 21011202220.

The previous prime is 21011202209. The next prime is 21011202229. The reversal of 21011202221 is 12220211012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18987462025 + 2023740196 = 137795^2 + 44986^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011202221 - 2¹⁸ = 21010940077 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21011202196 and 21011202205.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011202229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505601110 + 10505601111.

It is an arithmetic number, because the mean of its divisors is an integer number (10505601111).

Almost surely, 2^21011202221 is an apocalyptic number.

It is an amenable number.

21011202221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011202221 is an equidigital number, since it uses as much as digits as its factorization.

21011202221 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 14.

Adding to 21011202221 its reverse (12220211012), we get a palindrome (33231413233).

The spelling of 21011202221 in words is "twenty-one billion, eleven million, two hundred two thousand, two hundred twenty-one".