21855643 has 8 divisors (see below), whose sum is σ = 23284800. Its totient is φ = 20454408.

The previous prime is 21855623. The next prime is 21855649. The reversal of 21855643 is 34655812.

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 21855643 - 2⁹ = 21855131 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21855599 and 21855608.

It is not an unprimeable number, because it can be changed into a prime (21855649) 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, 5353 + ... + 8506.

It is an arithmetic number, because the mean of its divisors is an integer number (2910600).

Almost surely, 2^21855643 is an apocalyptic number.

21855643 is a deficient number, since it is larger than the sum of its proper divisors (1429157).

21855643 is a wasteful number, since it uses less digits than its factorization.

21855643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13961.

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

The square root of 21855643 is about 4675.0019251333. The cubic root of 21855643 is about 279.5897179879.

The spelling of 21855643 in words is "twenty-one million, eight hundred fifty-five thousand, six hundred forty-three".