21042903 has 24 divisors (see below), whose sum is σ = 32823792. Its totient is φ = 11956224.

The previous prime is 21042883. The next prime is 21042911. The reversal of 21042903 is 30924012.

It is not a de Polignac number, because 21042903 - 2⁶ = 21042839 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a self number, because there is not a number n which added to its sum of digits gives 21042903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042913) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 37501 + ... + 38057.

It is an arithmetic number, because the mean of its divisors is an integer number (1367658).

Almost surely, 2^21042903 is an apocalyptic number.

21042903 is a deficient number, since it is larger than the sum of its proper divisors (11780889).

21042903 is a wasteful number, since it uses less digits than its factorization.

21042903 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 831 (or 824 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21042903 is about 4587.2544075950. The cubic root of 21042903 is about 276.0801725714.

Adding to 21042903 its reverse (30924012), we get a palindrome (51966915).

It can be divided in two parts, 21042 and 903, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21042903 in words is "twenty-one million, forty-two thousand, nine hundred three".