21005543503 has 4 divisors (see below), whose sum is σ = 24006335440. Its totient is φ = 18004751568.

The previous prime is 21005543459. The next prime is 21005543521. The reversal of 21005543503 is 30534550012.

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 21005543503 - 2¹⁷ = 21005412431 is a prime.

It is a super-2 number, since 2×21005543503² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005543563) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1500395958 + ... + 1500395971.

It is an arithmetic number, because the mean of its divisors is an integer number (6001583860).

Almost surely, 2^21005543503 is an apocalyptic number.

21005543503 is a deficient number, since it is larger than the sum of its proper divisors (3000791937).

21005543503 is an equidigital number, since it uses as much as digits as its factorization.

21005543503 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3000791936.

The product of its (nonzero) digits is 9000, while the sum is 28.

The spelling of 21005543503 in words is "twenty-one billion, five million, five hundred forty-three thousand, five hundred three".