21255210173 has 2 divisors, whose sum is σ = 21255210174. Its totient is φ = 21255210172.

The previous prime is 21255210167. The next prime is 21255210227. The reversal of 21255210173 is 37101255212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11179467289 + 10075742884 = 105733^2 + 100378^2 .

It is a cyclic number.

It is not a de Polignac number, because 21255210173 - 2¹⁰ = 21255209149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21255210673) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10627605086 + 10627605087.

It is an arithmetic number, because the mean of its divisors is an integer number (10627605087).

Almost surely, 2^21255210173 is an apocalyptic number.

It is an amenable number.

21255210173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21255210173 is an equidigital number, since it uses as much as digits as its factorization.

21255210173 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4200, while the sum is 29.

Adding to 21255210173 its reverse (37101255212), we get a palindrome (58356465385).

The spelling of 21255210173 in words is "twenty-one billion, two hundred fifty-five million, two hundred ten thousand, one hundred seventy-three".