21426 has 8 divisors (see below), whose sum is σ = 42864. Its totient is φ = 7140.

The previous prime is 21419. The next prime is 21433. The reversal of 21426 is 62412.

21426 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (21419) and next prime (21433).

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

21426 is an admirable number.

It is a Curzon number.

It is an unprimeable number.

21426 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1780 + ... + 1791.

It is an arithmetic number, because the mean of its divisors is an integer number (5358).

2²¹⁴²⁶ is an apocalyptic number.

21426 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21432).

21426 is a wasteful number, since it uses less digits than its factorization.

21426 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3576.

The product of its digits is 96, while the sum is 15.

The square root of 21426 is about 146.3762275781. The cubic root of 21426 is about 27.7745501435.

Adding to 21426 its reverse (62412), we get a palindrome (83838).

The spelling of 21426 in words is "twenty-one thousand, four hundred twenty-six".