21768823 has 4 divisors (see below), whose sum is σ = 23049360. Its totient is φ = 20488288.

The previous prime is 21768811. The next prime is 21768847. The reversal of 21768823 is 32886712.

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

It is a cyclic number.

It is not a de Polignac number, because 21768823 - 2²¹ = 19671671 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 (21768853) 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 3 ways as a sum of consecutive naturals, for example, 640243 + ... + 640276.

It is an arithmetic number, because the mean of its divisors is an integer number (5762340).

Almost surely, 2^21768823 is an apocalyptic number.

21768823 is a deficient number, since it is larger than the sum of its proper divisors (1280537).

21768823 is a wasteful number, since it uses less digits than its factorization.

21768823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1280536.

The product of its digits is 32256, while the sum is 37.

The square root of 21768823 is about 4665.7071275424. The cubic root of 21768823 is about 279.2190098728.

The spelling of 21768823 in words is "twenty-one million, seven hundred sixty-eight thousand, eight hundred twenty-three".