21543685 has 4 divisors (see below), whose sum is σ = 25852428. Its totient is φ = 17234944.

The previous prime is 21543679. The next prime is 21543689. The reversal of 21543685 is 58634512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2411809 + 19131876 = 1553^2 + 4374^2 .

It is a cyclic number.

It is not a de Polignac number, because 21543685 - 2³ = 21543677 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21543685.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21543689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2154364 + ... + 2154373.

It is an arithmetic number, because the mean of its divisors is an integer number (6463107).

Almost surely, 2^21543685 is an apocalyptic number.

It is an amenable number.

21543685 is a deficient number, since it is larger than the sum of its proper divisors (4308743).

21543685 is an equidigital number, since it uses as much as digits as its factorization.

21543685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4308742.

The product of its digits is 28800, while the sum is 34.

The square root of 21543685 is about 4641.5175320147. The cubic root of 21543685 is about 278.2530906011.

The spelling of 21543685 in words is "twenty-one million, five hundred forty-three thousand, six hundred eighty-five".