21505632439 has 2 divisors, whose sum is σ = 21505632440. Its totient is φ = 21505632438.

The previous prime is 21505632437. The next prime is 21505632443. The reversal of 21505632439 is 93423650512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21505632439 - 2¹ = 21505632437 is a prime.

Together with 21505632437, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21505632437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752816219 + 10752816220.

It is an arithmetic number, because the mean of its divisors is an integer number (10752816220).

Almost surely, 2^21505632439 is an apocalyptic number.

21505632439 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505632439 is an equidigital number, since it uses as much as digits as its factorization.

21505632439 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 194400, while the sum is 40.

The spelling of 21505632439 in words is "twenty-one billion, five hundred five million, six hundred thirty-two thousand, four hundred thirty-nine".