21303 has 10 divisors (see below), whose sum is σ = 31944. Its totient is φ = 14148.

The previous prime is 21283. The next prime is 21313. The reversal of 21303 is 30312.

It is a happy number.

It is not a de Polignac number, because 21303 - 2¹² = 17207 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a nialpdrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21313) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 51 + ... + 212.

2²¹³⁰³ is an apocalyptic number.

21303 is a deficient number, since it is larger than the sum of its proper divisors (10641).

21303 is an equidigital number, since it uses as much as digits as its factorization.

21303 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275 (or 266 counting only the distinct ones).

The product of its (nonzero) digits is 18, while the sum is 9.

The square root of 21303 is about 145.9554726620. The cubic root of 21303 is about 27.7212997648.

Adding to 21303 its product of nonzero digits (18), we get a triangular number (21321 = T₂₀₆).

Adding to 21303 its reverse (30312), we get a palindrome (51615).

Subtracting 21303 from its reverse (30312), we obtain a palindrome (9009).

It can be divided in two parts, 21 and 303, that added together give a square (324 = 18²).

The spelling of 21303 in words is "twenty-one thousand, three hundred three", and thus it is an iban number.