21775823 has 2 divisors, whose sum is σ = 21775824. Its totient is φ = 21775822.

The previous prime is 21775811. The next prime is 21775837. The reversal of 21775823 is 32857712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21775823 - 2⁴ = 21775807 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21775123) 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 as a sum of consecutive naturals, namely, 10887911 + 10887912.

It is an arithmetic number, because the mean of its divisors is an integer number (10887912).

Almost surely, 2^21775823 is an apocalyptic number.

21775823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21775823 is an equidigital number, since it uses as much as digits as its factorization.

21775823 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23520, while the sum is 35.

The square root of 21775823 is about 4666.4572214904. The cubic root of 21775823 is about 279.2489352942.

It can be divided in two parts, 2177 and 5823, that added together give a cube (8000 = 20³).

The spelling of 21775823 in words is "twenty-one million, seven hundred seventy-five thousand, eight hundred twenty-three".