21072543 has 4 divisors (see below), whose sum is σ = 28096728. Its totient is φ = 14048360.

The previous prime is 21072533. The next prime is 21072551. The reversal of 21072543 is 34527012.

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 21072543 - 2⁹ = 21072031 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21072523) 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, 3512088 + ... + 3512093.

It is an arithmetic number, because the mean of its divisors is an integer number (7024182).

Almost surely, 2^21072543 is an apocalyptic number.

21072543 is a deficient number, since it is larger than the sum of its proper divisors (7024185).

21072543 is an equidigital number, since it uses as much as digits as its factorization.

21072543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7024184.

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 21072543 is about 4590.4839614141. The cubic root of 21072543 is about 276.2097360835.

Adding to 21072543 its reverse (34527012), we get a palindrome (55599555).

The spelling of 21072543 in words is "twenty-one million, seventy-two thousand, five hundred forty-three".