21537543 has 8 divisors (see below), whose sum is σ = 29001456. Its totient is φ = 14216000.

The previous prime is 21537541. The next prime is 21537547. The reversal of 21537543 is 34573512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21537543 - 2¹ = 21537541 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21537543.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21537541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35238 + ... + 35843.

It is an arithmetic number, because the mean of its divisors is an integer number (3625182).

Almost surely, 2^21537543 is an apocalyptic number.

21537543 is a deficient number, since it is larger than the sum of its proper divisors (7463913).

21537543 is a wasteful number, since it uses less digits than its factorization.

21537543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71185.

The product of its digits is 12600, while the sum is 30.

The square root of 21537543 is about 4640.8558477936. The cubic root of 21537543 is about 278.2266452194.

The spelling of 21537543 in words is "twenty-one million, five hundred thirty-seven thousand, five hundred forty-three".