21726820309 has 4 divisors (see below), whose sum is σ = 21937760416. Its totient is φ = 21515880204.

The previous prime is 21726820307. The next prime is 21726820337. The reversal of 21726820309 is 90302862712.

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 21726820309 - 2¹ = 21726820307 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 (21726820307) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105469899 + ... + 105470104.

It is an arithmetic number, because the mean of its divisors is an integer number (5484440104).

Almost surely, 2^21726820309 is an apocalyptic number.

It is an amenable number.

21726820309 is a deficient number, since it is larger than the sum of its proper divisors (210940107).

21726820309 is a wasteful number, since it uses less digits than its factorization.

21726820309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 210940106.

The product of its (nonzero) digits is 72576, while the sum is 40.

The spelling of 21726820309 in words is "twenty-one billion, seven hundred twenty-six million, eight hundred twenty thousand, three hundred nine".