21505510489 has 2 divisors, whose sum is σ = 21505510490. Its totient is φ = 21505510488.

The previous prime is 21505510471. The next prime is 21505510573. The reversal of 21505510489 is 98401550512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16476289600 + 5029220889 = 128360^2 + 70917^2 .

It is a cyclic number.

It is not a de Polignac number, because 21505510489 - 2¹¹ = 21505508441 is a prime.

It is not a weakly prime, because it can be changed into another prime (21505514489) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752755244 + 10752755245.

It is an arithmetic number, because the mean of its divisors is an integer number (10752755245).

Almost surely, 2^21505510489 is an apocalyptic number.

It is an amenable number.

21505510489 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505510489 is an equidigital number, since it uses as much as digits as its factorization.

21505510489 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72000, while the sum is 40.

The spelling of 21505510489 in words is "twenty-one billion, five hundred five million, five hundred ten thousand, four hundred eighty-nine".