21011222161 has 2 divisors, whose sum is σ = 21011222162. Its totient is φ = 21011222160.

The previous prime is 21011222159. The next prime is 21011222171. The reversal of 21011222161 is 16122211012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16465765761 + 4545456400 = 128319^2 + 67420^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011222161 - 2¹ = 21011222159 is a prime.

Together with 21011222159, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21011222101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505611080 + 10505611081.

It is an arithmetic number, because the mean of its divisors is an integer number (10505611081).

Almost surely, 2^21011222161 is an apocalyptic number.

It is an amenable number.

21011222161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011222161 is an equidigital number, since it uses as much as digits as its factorization.

21011222161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 19.

Adding to 21011222161 its reverse (16122211012), we get a palindrome (37133433173).

The spelling of 21011222161 in words is "twenty-one billion, eleven million, two hundred twenty-two thousand, one hundred sixty-one".