20403 has 6 divisors (see below), whose sum is σ = 29484. Its totient is φ = 13596.

The previous prime is 20399. The next prime is 20407. The reversal of 20403 is 30402.

It is an interprime number because it is at equal distance from previous prime (20399) and next prime (20407).

It is not a de Polignac number, because 20403 - 2² = 20399 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2267 = 20403 / (2 + 0 + 4 + 0 + 3).

20403 is a lucky number.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (20407) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1125 + ... + 1142.

It is an arithmetic number, because the mean of its divisors is an integer number (4914).

2²⁰⁴⁰³ is an apocalyptic number.

20403 is a deficient number, since it is larger than the sum of its proper divisors (9081).

20403 is a wasteful number, since it uses less digits than its factorization.

20403 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2273 (or 2270 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 9.

The square root of 20403 is about 142.8390702854. The cubic root of 20403 is about 27.3252835043.

Adding to 20403 its reverse (30402), we get a palindrome (50805).

Subtracting 20403 from its reverse (30402), we obtain a palindrome (9999).

The spelling of 20403 in words is "twenty thousand, four hundred three", and thus it is an iban number.