21242503 has 4 divisors (see below), whose sum is σ = 22492080. Its totient is φ = 19992928.

The previous prime is 21242491. The next prime is 21242509. The reversal of 21242503 is 30524212.

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 21242503 - 2⁹ = 21241991 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 (21242509) 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, 624763 + ... + 624796.

It is an arithmetic number, because the mean of its divisors is an integer number (5623020).

Almost surely, 2^21242503 is an apocalyptic number.

21242503 is a deficient number, since it is larger than the sum of its proper divisors (1249577).

21242503 is a wasteful number, since it uses less digits than its factorization.

21242503 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1249576.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21242503 is about 4608.9589930916. The cubic root of 21242503 is about 276.9503358158.

Adding to 21242503 its reverse (30524212), we get a palindrome (51766715).

The spelling of 21242503 in words is "twenty-one million, two hundred forty-two thousand, five hundred three".