21306535819 has 4 divisors (see below), whose sum is σ = 21802036696. Its totient is φ = 20811034944.

The previous prime is 21306535807. The next prime is 21306535843. The reversal of 21306535819 is 91853560312.

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

It is a cyclic number.

It is not a de Polignac number, because 21306535819 - 2⁵ = 21306535787 is a prime.

It is a super-2 number, since 2×21306535819² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (43), and also a Moran number because the ratio is a prime number: 495500833 = 21306535819 / (2 + 1 + 3 + 0 + 6 + 5 + 3 + 5 + 8 + 1 + 9).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21306505819) 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, 247750374 + ... + 247750459.

It is an arithmetic number, because the mean of its divisors is an integer number (5450509174).

Almost surely, 2^21306535819 is an apocalyptic number.

21306535819 is a deficient number, since it is larger than the sum of its proper divisors (495500877).

21306535819 is an equidigital number, since it uses as much as digits as its factorization.

21306535819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 495500876.

The product of its (nonzero) digits is 194400, while the sum is 43.

The spelling of 21306535819 in words is "twenty-one billion, three hundred six million, five hundred thirty-five thousand, eight hundred nineteen".