21493543 has 4 divisors (see below), whose sum is σ = 21536280. Its totient is φ = 21450808.

The previous prime is 21493531. The next prime is 21493547. The reversal of 21493543 is 34539412.

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 21493543 - 2¹³ = 21485351 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21493547) 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, 20605 + ... + 21622.

It is an arithmetic number, because the mean of its divisors is an integer number (5384070).

Almost surely, 2^21493543 is an apocalyptic number.

21493543 is a deficient number, since it is larger than the sum of its proper divisors (42737).

21493543 is an equidigital number, since it uses as much as digits as its factorization.

21493543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42736.

The product of its digits is 12960, while the sum is 31.

The square root of 21493543 is about 4636.1129192460. The cubic root of 21493543 is about 278.0370488725.

The spelling of 21493543 in words is "twenty-one million, four hundred ninety-three thousand, five hundred forty-three".