21543603 has 16 divisors (see below), whose sum is σ = 29348256. Its totient is φ = 14054400.

The previous prime is 21543593. The next prime is 21543611. The reversal of 21543603 is 30634512.

It is a happy number.

It is not a de Polignac number, because 21543603 - 2⁹ = 21543091 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21543653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29025 + ... + 29757.

It is an arithmetic number, because the mean of its divisors is an integer number (1834266).

Almost surely, 2^21543603 is an apocalyptic number.

21543603 is a deficient number, since it is larger than the sum of its proper divisors (7804653).

21543603 is a wasteful number, since it uses less digits than its factorization.

21543603 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 934.

The product of its (nonzero) digits is 2160, while the sum is 24.

The square root of 21543603 is about 4641.5086986884. The cubic root of 21543603 is about 278.2527375698.

Subtracting 21543603 from its reverse (30634512), we obtain a palindrome (9090909).

The spelling of 21543603 in words is "twenty-one million, five hundred forty-three thousand, six hundred three".