21711 has 4 divisors (see below), whose sum is σ = 28952. Its totient is φ = 14472.

The previous prime is 21701. The next prime is 21713. The reversal of 21711 is 11712.

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

It is not a de Polignac number, because 21711 - 2⁶ = 21647 is a prime.

It is an Ulam number.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21713) 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, 3616 + ... + 3621.

It is an arithmetic number, because the mean of its divisors is an integer number (7238).

2²¹⁷¹¹ is an apocalyptic number.

21711 is a deficient number, since it is larger than the sum of its proper divisors (7241).

21711 is an equidigital number, since it uses as much as digits as its factorization.

21711 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7240.

The product of its digits is 14, while the sum is 12.

The square root of 21711 is about 147.3465303290. The cubic root of 21711 is about 27.8971567355.

Subtracting from 21711 its reverse (11712), we obtain a palindrome (9999).

The spelling of 21711 in words is "twenty-one thousand, seven hundred eleven", and thus it is an iban number.