21055823 has 4 divisors (see below), whose sum is σ = 21123408. Its totient is φ = 20988240.

The previous prime is 21055817. The next prime is 21055829. The reversal of 21055823 is 32855012.

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

It is an interprime number because it is at equal distance from previous prime (21055817) and next prime (21055829).

It is a cyclic number.

It is not a de Polignac number, because 21055823 - 2⁴ = 21055807 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21055792 and 21055801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21055829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33323 + ... + 33948.

It is an arithmetic number, because the mean of its divisors is an integer number (5280852).

Almost surely, 2^21055823 is an apocalyptic number.

21055823 is a deficient number, since it is larger than the sum of its proper divisors (67585).

21055823 is an equidigital number, since it uses as much as digits as its factorization.

21055823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67584.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 21055823 is about 4588.6624412785. The cubic root of 21055823 is about 276.1366639224.

The spelling of 21055823 in words is "twenty-one million, fifty-five thousand, eight hundred twenty-three".