21724112721 has 4 divisors (see below), whose sum is σ = 28965483632. Its totient is φ = 14482741812.

The previous prime is 21724112701. The next prime is 21724112731. The reversal of 21724112721 is 12721142712.

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 not a de Polignac number, because 21724112721 - 2²³ = 21715724113 is a prime.

It is a super-3 number, since 3×21724112721³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21724112701) 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, 3620685451 + ... + 3620685456.

It is an arithmetic number, because the mean of its divisors is an integer number (7241370908).

Almost surely, 2^21724112721 is an apocalyptic number.

It is an amenable number.

21724112721 is a deficient number, since it is larger than the sum of its proper divisors (7241370911).

21724112721 is an equidigital number, since it uses as much as digits as its factorization.

21724112721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7241370910.

The product of its digits is 3136, while the sum is 30.

The spelling of 21724112721 in words is "twenty-one billion, seven hundred twenty-four million, one hundred twelve thousand, seven hundred twenty-one".