21903 has 12 divisors (see below), whose sum is σ = 34200. Its totient is φ = 12432.

The previous prime is 21893. The next prime is 21911. The reversal of 21903 is 30912.

It is a Cunningham number, because it is equal to 148²-1.

It is not a de Polignac number, because 21903 - 2⁵ = 21871 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21943) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 73 + ... + 221.

It is an arithmetic number, because the mean of its divisors is an integer number (2850).

2²¹⁹⁰³ is an apocalyptic number.

21903 is a deficient number, since it is larger than the sum of its proper divisors (12297).

21903 is a wasteful number, since it uses less digits than its factorization.

21903 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 166 (or 159 counting only the distinct ones).

The product of its (nonzero) digits is 54, while the sum is 15.

The square root of 21903 is about 147.9966215831. The cubic root of 21903 is about 27.9791511464.

Subtracting 21903 from its reverse (30912), we obtain a palindrome (9009).

The spelling of 21903 in words is "twenty-one thousand, nine hundred three".