21685726319 has 4 divisors (see below), whose sum is σ = 22009393944. Its totient is φ = 21362058696.

The previous prime is 21685726277. The next prime is 21685726339. The reversal of 21685726319 is 91362758612.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21685726319 is a prime.

It is a super-2 number, since 2×21685726319² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21685726339) 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, 161833712 + ... + 161833845.

It is an arithmetic number, because the mean of its divisors is an integer number (5502348486).

Almost surely, 2^21685726319 is an apocalyptic number.

21685726319 is a deficient number, since it is larger than the sum of its proper divisors (323667625).

21685726319 is an equidigital number, since it uses as much as digits as its factorization.

21685726319 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 323667624.

The product of its digits is 1088640, while the sum is 50.

The spelling of 21685726319 in words is "twenty-one billion, six hundred eighty-five million, seven hundred twenty-six thousand, three hundred nineteen".