21000311221 has 2 divisors, whose sum is σ = 21000311222. Its totient is φ = 21000311220.

The previous prime is 21000311209. The next prime is 21000311249. The reversal of 21000311221 is 12211300012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20951115025 + 49196196 = 144745^2 + 7014^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000311221 - 2¹¹ = 21000309173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000311821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500155610 + 10500155611.

It is an arithmetic number, because the mean of its divisors is an integer number (10500155611).

Almost surely, 2^21000311221 is an apocalyptic number.

It is an amenable number.

21000311221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000311221 is an equidigital number, since it uses as much as digits as its factorization.

21000311221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24, while the sum is 13.

Adding to 21000311221 its reverse (12211300012), we get a palindrome (33211611233).

The spelling of 21000311221 in words is "twenty-one billion, three hundred eleven thousand, two hundred twenty-one".