21499823 has 2 divisors, whose sum is σ = 21499824. Its totient is φ = 21499822.

The previous prime is 21499813. The next prime is 21499837. The reversal of 21499823 is 32899412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21499823 - 2¹⁴ = 21483439 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21499813) 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, 10749911 + 10749912.

It is an arithmetic number, because the mean of its divisors is an integer number (10749912).

Almost surely, 2^21499823 is an apocalyptic number.

21499823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21499823 is an equidigital number, since it uses as much as digits as its factorization.

21499823 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 38.

The square root of 21499823 is about 4636.7901613077. The cubic root of 21499823 is about 278.0641252622.

It can be divided in two parts, 21499 and 823, that added together give a palindrome (22322).

The spelling of 21499823 in words is "twenty-one million, four hundred ninety-nine thousand, eight hundred twenty-three".