21809553613 has 2 divisors, whose sum is σ = 21809553614. Its totient is φ = 21809553612.

The previous prime is 21809553611. The next prime is 21809553629. The reversal of 21809553613 is 31635590812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17281205764 + 4528347849 = 131458^2 + 67293^2 .

It is a cyclic number.

It is not a de Polignac number, because 21809553613 - 2¹ = 21809553611 is a prime.

Together with 21809553611, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21809553613.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21809553611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10904776806 + 10904776807.

It is an arithmetic number, because the mean of its divisors is an integer number (10904776807).

Almost surely, 2^21809553613 is an apocalyptic number.

It is an amenable number.

21809553613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21809553613 is an equidigital number, since it uses as much as digits as its factorization.

21809553613 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 43.

The spelling of 21809553613 in words is "twenty-one billion, eight hundred nine million, five hundred fifty-three thousand, six hundred thirteen".