21367 has 4 divisors (see below), whose sum is σ = 22320. Its totient is φ = 20416.

The previous prime is 21347. The next prime is 21377. The reversal of 21367 is 76312.

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 21367 - 2¹¹ = 19319 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 (21317) 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, 442 + ... + 487.

It is an arithmetic number, because the mean of its divisors is an integer number (5580).

2²¹³⁶⁷ is an apocalyptic number.

21367 is a deficient number, since it is larger than the sum of its proper divisors (953).

21367 is an equidigital number, since it uses as much as digits as its factorization.

21367 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 952.

The product of its digits is 252, while the sum is 19.

The square root of 21367 is about 146.1745531890. The cubic root of 21367 is about 27.7490327829.

Subtracting from 21367 its product of digits (252), we obtain a triangular number (21115 = T₂₀₅).

Adding to 21367 its reverse (76312), we get a palindrome (97679).

Subtracting 21367 from its reverse (76312), we obtain a palindrome (54945).

It can be divided in two parts, 2 and 1367, that added together give a square (1369 = 37²).

The spelling of 21367 in words is "twenty-one thousand, three hundred sixty-seven".