21543605 has 16 divisors (see below), whose sum is σ = 26915328. Its totient is φ = 16536000.

The previous prime is 21543593. The next prime is 21543611. The reversal of 21543605 is 50634512.

It is not a de Polignac number, because 21543605 - 2⁴ = 21543589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19775 + ... + 20835.

It is an arithmetic number, because the mean of its divisors is an integer number (1682208).

Almost surely, 2^21543605 is an apocalyptic number.

It is an amenable number.

21543605 is a deficient number, since it is larger than the sum of its proper divisors (5371723).

21543605 is a wasteful number, since it uses less digits than its factorization.

21543605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1228.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21543605 is about 4641.5089141356. The cubic root of 21543605 is about 278.2527461804.

The spelling of 21543605 in words is "twenty-one million, five hundred forty-three thousand, six hundred five".