21268683509 has 4 divisors (see below), whose sum is σ = 21269245260. Its totient is φ = 21268121760.

The previous prime is 21268683473. The next prime is 21268683547. The reversal of 21268683509 is 90538686212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11337564484 + 9931119025 = 106478^2 + 99655^2 .

It is a cyclic number.

It is not a de Polignac number, because 21268683509 - 2¹⁶ = 21268617973 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 (21268683589) 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, 219632 + ... + 301289.

It is an arithmetic number, because the mean of its divisors is an integer number (5317311315).

Almost surely, 2^21268683509 is an apocalyptic number.

It is an amenable number.

21268683509 is a deficient number, since it is larger than the sum of its proper divisors (561751).

21268683509 is an equidigital number, since it uses as much as digits as its factorization.

21268683509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 561750.

The product of its (nonzero) digits is 1244160, while the sum is 50.

The spelling of 21268683509 in words is "twenty-one billion, two hundred sixty-eight million, six hundred eighty-three thousand, five hundred nine".