21423 has 8 divisors (see below), whose sum is σ = 29488. Its totient is φ = 13824.

The previous prime is 21419. The next prime is 21433. The reversal of 21423 is 32412.

21423 is an esthetic number in base 9, because in such base its adjacent digits differ by 1.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21423 - 2² = 21419 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 21399 and 21408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21433) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15 + ... + 207.

It is an arithmetic number, because the mean of its divisors is an integer number (3686).

2²¹⁴²³ is an apocalyptic number.

21423 is a deficient number, since it is larger than the sum of its proper divisors (8065).

21423 is a wasteful number, since it uses less digits than its factorization.

21423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 233.

The product of its digits is 48, while the sum is 12.

The square root of 21423 is about 146.3659796537. The cubic root of 21423 is about 27.7732537818.

Adding to 21423 its reverse (32412), we get a palindrome (53835).

It can be divided in two parts, 2142 and 3, that added together give a triangular number (2145 = T₆₅).

The spelling of 21423 in words is "twenty-one thousand, four hundred twenty-three", and thus it is an iban number.