21212221061 has 2 divisors, whose sum is σ = 21212221062. Its totient is φ = 21212221060.

The previous prime is 21212221049. The next prime is 21212221117. The reversal of 21212221061 is 16012221212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20943588961 + 268632100 = 144719^2 + 16390^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21212221061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21212223061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606110530 + 10606110531.

It is an arithmetic number, because the mean of its divisors is an integer number (10606110531).

Almost surely, 2^21212221061 is an apocalyptic number.

It is an amenable number.

21212221061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212221061 is an equidigital number, since it uses as much as digits as its factorization.

21212221061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 20.

Adding to 21212221061 its reverse (16012221212), we get a palindrome (37224442273).

The spelling of 21212221061 in words is "twenty-one billion, two hundred twelve million, two hundred twenty-one thousand, sixty-one".