21293 has 4 divisors (see below), whose sum is σ = 21600. Its totient is φ = 20988.

The previous prime is 21283. The next prime is 21313. The reversal of 21293 is 39212.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21293 - 2⁴ = 21277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21283) 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, 8 + ... + 206.

It is an arithmetic number, because the mean of its divisors is an integer number (5400).

2²¹²⁹³ is an apocalyptic number.

It is an amenable number.

21293 is a deficient number, since it is larger than the sum of its proper divisors (307).

21293 is a wasteful number, since it uses less digits than its factorization.

21293 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 306.

The product of its digits is 108, while the sum is 17.

The square root of 21293 is about 145.9212116178. The cubic root of 21293 is about 27.7169614652.

The spelling of 21293 in words is "twenty-one thousand, two hundred ninety-three".