21201021173 has 2 divisors, whose sum is σ = 21201021174. Its totient is φ = 21201021172.

The previous prime is 21201021143. The next prime is 21201021211. The reversal of 21201021173 is 37112010212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20275766449 + 925254724 = 142393^2 + 30418^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201021173 - 2⁸ = 21201020917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201021133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600510586 + 10600510587.

It is an arithmetic number, because the mean of its divisors is an integer number (10600510587).

Almost surely, 2^21201021173 is an apocalyptic number.

It is an amenable number.

21201021173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201021173 is an equidigital number, since it uses as much as digits as its factorization.

21201021173 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 168, while the sum is 20.

Adding to 21201021173 its reverse (37112010212), we get a palindrome (58313031385).

The spelling of 21201021173 in words is "twenty-one billion, two hundred one million, twenty-one thousand, one hundred seventy-three".