21685843 has 8 divisors (see below), whose sum is σ = 22288896. Its totient is φ = 21086400.

The previous prime is 21685837. The next prime is 21685861. The reversal of 21685843 is 34858612.

It is a happy number.

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 21685843 - 2²¹ = 19588691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21683843) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 15013 + ... + 16393.

It is an arithmetic number, because the mean of its divisors is an integer number (2786112).

Almost surely, 2^21685843 is an apocalyptic number.

21685843 is a deficient number, since it is larger than the sum of its proper divisors (603053).

21685843 is a wasteful number, since it uses less digits than its factorization.

21685843 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1805.

The product of its digits is 46080, while the sum is 37.

The square root of 21685843 is about 4656.8060943097. The cubic root of 21685843 is about 278.8637756035.

The spelling of 21685843 in words is "twenty-one million, six hundred eighty-five thousand, eight hundred forty-three".