21823643 has 4 divisors (see below), whose sum is σ = 21833760. Its totient is φ = 21813528.

The previous prime is 21823639. The next prime is 21823663. The reversal of 21823643 is 34632812.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21823643 - 2² = 21823639 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21823663) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 380 + ... + 6617.

It is an arithmetic number, because the mean of its divisors is an integer number (5458440).

Almost surely, 2^21823643 is an apocalyptic number.

21823643 is a deficient number, since it is larger than the sum of its proper divisors (10117).

21823643 is an equidigital number, since it uses as much as digits as its factorization.

21823643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10116.

The product of its digits is 6912, while the sum is 29.

The square root of 21823643 is about 4671.5782129811. The cubic root of 21823643 is about 279.4531973181.

The spelling of 21823643 in words is "twenty-one million, eight hundred twenty-three thousand, six hundred forty-three".