21221211173 has 2 divisors, whose sum is σ = 21221211174. Its totient is φ = 21221211172.

The previous prime is 21221211149. The next prime is 21221211217. The reversal of 21221211173 is 37111212212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11937310564 + 9283900609 = 109258^2 + 96353^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221211173 - 2²⁸ = 20952775717 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221211113) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610605586 + 10610605587.

It is an arithmetic number, because the mean of its divisors is an integer number (10610605587).

Almost surely, 2^21221211173 is an apocalyptic number.

It is an amenable number.

21221211173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221211173 is an equidigital number, since it uses as much as digits as its factorization.

21221211173 is an evil number, because the sum of its binary digits is even.

The product of its digits is 336, while the sum is 23.

Adding to 21221211173 its reverse (37111212212), we get a palindrome (58332423385).

The spelling of 21221211173 in words is "twenty-one billion, two hundred twenty-one million, two hundred eleven thousand, one hundred seventy-three".