21143605 has 16 divisors (see below), whose sum is σ = 29078784. Its totient is φ = 14457600.

The previous prime is 21143579. The next prime is 21143609. The reversal of 21143605 is 50634112.

It is not a de Polignac number, because 21143605 - 2⁷ = 21143477 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21143609) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17005 + ... + 18205.

It is an arithmetic number, because the mean of its divisors is an integer number (1817424).

Almost surely, 2^21143605 is an apocalyptic number.

It is an amenable number.

21143605 is a deficient number, since it is larger than the sum of its proper divisors (7935179).

21143605 is a wasteful number, since it uses less digits than its factorization.

21143605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1716.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21143605 is about 4598.2175894579. The cubic root of 21143605 is about 276.5198709977.

Adding to 21143605 its reverse (50634112), we get a palindrome (71777717).

The spelling of 21143605 in words is "twenty-one million, one hundred forty-three thousand, six hundred five".