21003403 has 4 divisors (see below), whose sum is σ = 21015648. Its totient is φ = 20991160.

The previous prime is 21003397. The next prime is 21003413. The reversal of 21003403 is 30430012.

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 21003403 - 2⁵ = 21003371 is a prime.

It is a super-2 number, since 2×21003403² = 882285875160818, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21003413) 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, 3028 + ... + 7153.

It is an arithmetic number, because the mean of its divisors is an integer number (5253912).

Almost surely, 2^21003403 is an apocalyptic number.

21003403 is a deficient number, since it is larger than the sum of its proper divisors (12245).

21003403 is a wasteful number, since it uses less digits than its factorization.

21003403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12244.

The product of its (nonzero) digits is 72, while the sum is 13.

The square root of 21003403 is about 4582.9469776553. The cubic root of 21003403 is about 275.9073194030.

Adding to 21003403 its reverse (30430012), we get a palindrome (51433415).

The spelling of 21003403 in words is "twenty-one million, three thousand, four hundred three".