21212020202221 has 2 divisors, whose sum is σ = 21212020202222. Its totient is φ = 21212020202220.

The previous prime is 21212020202209. The next prime is 21212020202287. The reversal of 21212020202221 is 12220202021212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19435850949321 + 1776169252900 = 4408611^2 + 1332730^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212020202221 - 2²³ = 21212011813613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21212020200221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606010101110 + 10606010101111.

It is an arithmetic number, because the mean of its divisors is an integer number (10606010101111).

Almost surely, 2^{21212020202221} is an apocalyptic number.

It is an amenable number.

21212020202221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212020202221 is an equidigital number, since it uses as much as digits as its factorization.

21212020202221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 19.

Adding to 21212020202221 its reverse (12220202021212), we get a palindrome (33432222223433).

The spelling of 21212020202221 in words is "twenty-one trillion, two hundred twelve billion, twenty million, two hundred two thousand, two hundred twenty-one".