21117543 has 4 divisors (see below), whose sum is σ = 28156728. Its totient is φ = 14078360.

The previous prime is 21117521. The next prime is 21117557. The reversal of 21117543 is 34571112.

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 21117543 - 2¹⁰ = 21116519 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21117563) 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, 3519588 + ... + 3519593.

It is an arithmetic number, because the mean of its divisors is an integer number (7039182).

Almost surely, 2^21117543 is an apocalyptic number.

21117543 is a deficient number, since it is larger than the sum of its proper divisors (7039185).

21117543 is an equidigital number, since it uses as much as digits as its factorization.

21117543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7039184.

The product of its digits is 840, while the sum is 24.

The square root of 21117543 is about 4595.3827914549. The cubic root of 21117543 is about 276.4062097760.

Adding to 21117543 its reverse (34571112), we get a palindrome (55688655).

The spelling of 21117543 in words is "twenty-one million, one hundred seventeen thousand, five hundred forty-three".