21530503 has 4 divisors (see below), whose sum is σ = 21557488. Its totient is φ = 21503520.

The previous prime is 21530497. The next prime is 21530513. The reversal of 21530503 is 30503512.

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 21530503 - 2⁵ = 21530471 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 (21530513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12258 + ... + 13903.

It is an arithmetic number, because the mean of its divisors is an integer number (5389372).

Almost surely, 2^21530503 is an apocalyptic number.

21530503 is a deficient number, since it is larger than the sum of its proper divisors (26985).

21530503 is an equidigital number, since it uses as much as digits as its factorization.

21530503 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26984.

The product of its (nonzero) digits is 450, while the sum is 19.

The square root of 21530503 is about 4640.0973050142. The cubic root of 21530503 is about 278.1963271675.

The spelling of 21530503 in words is "twenty-one million, five hundred thirty thousand, five hundred three".