11721 has 4 divisors (see below), whose sum is σ = 15632.
Its totient is φ = 7812.
The previous prime is 11719. The next prime is 11731. The reversal of 11721 is 12711.
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 11721 - 21 = 11719 is a prime.
It is a D-number.
It is a Duffinian number.
11721 is a lucky number.
It is a junction number, because it is equal to n+sod(n) for n = 11697 and 11706.
It is not an unprimeable number, because it can be changed into a prime (11701) 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, 1951 + ... + 1956.
It is an arithmetic number, because the mean of its divisors is an integer number (3908).
211721 is an apocalyptic number.
It is an amenable number.
11721 is a deficient number, since it is larger than the sum of its proper divisors (3911).
11721 is an equidigital number, since it uses as much as digits as its factorization.
11721 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 3910.
The product of its digits is 14, while the sum is 12.
The square root of 11721 is about 108.2635672791.
The cubic root of 11721 is about 22.7154610138.
Subtracting 11721 from its reverse (12711), we obtain a triangular number (990 = T44).
The spelling of 11721 in words is "eleven thousand, seven hundred twenty-one", and thus it is an iban number.