17421 has 4 divisors (see below), whose sum is σ = 23232. Its totient is φ = 11612.

The previous prime is 17419. The next prime is 17431. The reversal of 17421 is 12471.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12471 = 3 ⋅4157.

It is a cyclic number.

It is not a de Polignac number, because 17421 - 2¹ = 17419 is a prime.

It is a D-number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 17421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (17401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2901 + ... + 2906.

It is an arithmetic number, because the mean of its divisors is an integer number (5808).

2¹⁷⁴²¹ is an apocalyptic number.

It is an amenable number.

17421 is a deficient number, since it is larger than the sum of its proper divisors (5811).

17421 is an equidigital number, since it uses as much as digits as its factorization.

17421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5810.

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

The square root of 17421 is about 131.9886358745. The cubic root of 17421 is about 25.9233442378.

Adding to 17421 its reverse (12471), we get a palindrome (29892).

Subtracting from 17421 its reverse (12471), we obtain a triangular number (4950 = T₉₉).

The spelling of 17421 in words is "seventeen thousand, four hundred twenty-one", and thus it is an iban number.