21263 has 4 divisors (see below), whose sum is σ = 23208. Its totient is φ = 19320.

The previous prime is 21247. The next prime is 21269. The reversal of 21263 is 36212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21263 - 2⁴ = 21247 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 (21269) 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, 956 + ... + 977.

It is an arithmetic number, because the mean of its divisors is an integer number (5802).

2²¹²⁶³ is an apocalyptic number.

21263 is a deficient number, since it is larger than the sum of its proper divisors (1945).

21263 is a wasteful number, since it uses less digits than its factorization.

21263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1944.

The product of its digits is 72, while the sum is 14.

The square root of 21263 is about 145.8183801858. The cubic root of 21263 is about 27.7039384114.

Adding to 21263 its reverse (36212), we get a palindrome (57475).

The spelling of 21263 in words is "twenty-one thousand, two hundred sixty-three".