21359309509 has 4 divisors (see below), whose sum is σ = 21359630304. Its totient is φ = 21358988716.

The previous prime is 21359309501. The next prime is 21359309533. The reversal of 21359309509 is 90590395312.

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 21359309509 - 2³ = 21359309501 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21359309501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18937 + ... + 207550.

It is an arithmetic number, because the mean of its divisors is an integer number (5339907576).

Almost surely, 2^21359309509 is an apocalyptic number.

It is an amenable number.

21359309509 is a deficient number, since it is larger than the sum of its proper divisors (320795).

21359309509 is an equidigital number, since it uses as much as digits as its factorization.

21359309509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320794.

The product of its (nonzero) digits is 328050, while the sum is 46.

The spelling of 21359309509 in words is "twenty-one billion, three hundred fifty-nine million, three hundred nine thousand, five hundred nine".