21310128173 has 2 divisors, whose sum is σ = 21310128174. Its totient is φ = 21310128172.

The previous prime is 21310128157. The next prime is 21310128179. The reversal of 21310128173 is 37182101312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20069538889 + 1240589284 = 141667^2 + 35222^2 .

It is a cyclic number.

It is not a de Polignac number, because 21310128173 - 2⁴ = 21310128157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21310128179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655064086 + 10655064087.

It is an arithmetic number, because the mean of its divisors is an integer number (10655064087).

Almost surely, 2^21310128173 is an apocalyptic number.

It is an amenable number.

21310128173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21310128173 is an equidigital number, since it uses as much as digits as its factorization.

21310128173 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 29.

Adding to 21310128173 its reverse (37182101312), we get a palindrome (58492229485).

The spelling of 21310128173 in words is "twenty-one billion, three hundred ten million, one hundred twenty-eight thousand, one hundred seventy-three".