21305689609 has 4 divisors (see below), whose sum is σ = 21321843840. Its totient is φ = 21289535380.

The previous prime is 21305689571. The next prime is 21305689627. The reversal of 21305689609 is 90698650312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21305689609 - 2³¹ = 19158205961 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21305689649) 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 in 3 ways as a sum of consecutive naturals, for example, 8075137 + ... + 8077774.

It is an arithmetic number, because the mean of its divisors is an integer number (5330460960).

Almost surely, 2^21305689609 is an apocalyptic number.

It is an amenable number.

21305689609 is a deficient number, since it is larger than the sum of its proper divisors (16154231).

21305689609 is a wasteful number, since it uses less digits than its factorization.

21305689609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16154230.

The product of its (nonzero) digits is 699840, while the sum is 49.

The spelling of 21305689609 in words is "twenty-one billion, three hundred five million, six hundred eighty-nine thousand, six hundred nine".