21741 has 4 divisors (see below), whose sum is σ = 28992. Its totient is φ = 14492.

The previous prime is 21739. The next prime is 21751. The reversal of 21741 is 14712.

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 21741 - 2¹ = 21739 is a prime.

It is a D-number.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 21741.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21701) 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, 3621 + ... + 3626.

It is an arithmetic number, because the mean of its divisors is an integer number (7248).

2²¹⁷⁴¹ is an apocalyptic number.

It is an amenable number.

21741 is a deficient number, since it is larger than the sum of its proper divisors (7251).

21741 is an equidigital number, since it uses as much as digits as its factorization.

21741 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7250.

The product of its digits is 56, while the sum is 15.

The square root of 21741 is about 147.4482960227. The cubic root of 21741 is about 27.9100001408.

The spelling of 21741 in words is "twenty-one thousand, seven hundred forty-one", and thus it is an iban number.