21001122173 has 2 divisors, whose sum is σ = 21001122174. Its totient is φ = 21001122172.

The previous prime is 21001122073. The next prime is 21001122179. The reversal of 21001122173 is 37122110012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11932940644 + 9068181529 = 109238^2 + 95227^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001122173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21001122179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500561086 + 10500561087.

It is an arithmetic number, because the mean of its divisors is an integer number (10500561087).

Almost surely, 2^21001122173 is an apocalyptic number.

It is an amenable number.

21001122173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001122173 is an equidigital number, since it uses as much as digits as its factorization.

21001122173 is an evil number, because the sum of its binary digits is even.

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

Adding to 21001122173 its reverse (37122110012), we get a palindrome (58123232185).

The spelling of 21001122173 in words is "twenty-one billion, one million, one hundred twenty-two thousand, one hundred seventy-three".