21003653 has 12 divisors (see below), whose sum is σ = 24343872. Its totient is φ = 17968320.

The previous prime is 21003637. The next prime is 21003659. The reversal of 21003653 is 35630012.

It is not a de Polignac number, because 21003653 - 2⁴ = 21003637 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003659) 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 11 ways as a sum of consecutive naturals, for example, 125 + ... + 6482.

It is an arithmetic number, because the mean of its divisors is an integer number (2028656).

Almost surely, 2^21003653 is an apocalyptic number.

It is an amenable number.

21003653 is a deficient number, since it is larger than the sum of its proper divisors (3340219).

21003653 is a wasteful number, since it uses less digits than its factorization.

21003653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6652 (or 6635 counting only the distinct ones).

The product of its (nonzero) digits is 540, while the sum is 20.

The square root of 21003653 is about 4582.9742526006. The cubic root of 21003653 is about 275.9084140916.

Adding to 21003653 its reverse (35630012), we get a palindrome (56633665).

The spelling of 21003653 in words is "twenty-one million, three thousand, six hundred fifty-three".