21680823 has 4 divisors (see below), whose sum is σ = 28907768. Its totient is φ = 14453880.

The previous prime is 21680819. The next prime is 21680833. The reversal of 21680823 is 32808612.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21680823 - 2² = 21680819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680833) 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, 3613468 + ... + 3613473.

It is an arithmetic number, because the mean of its divisors is an integer number (7226942).

Almost surely, 2^21680823 is an apocalyptic number.

21680823 is a deficient number, since it is larger than the sum of its proper divisors (7226945).

21680823 is an equidigital number, since it uses as much as digits as its factorization.

21680823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7226944.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 21680823 is about 4656.2670670828. The cubic root of 21680823 is about 278.8422561236.

The spelling of 21680823 in words is "twenty-one million, six hundred eighty thousand, eight hundred twenty-three".