21285923 has 6 divisors (see below), whose sum is σ = 21488844. Its totient is φ = 21084896.

The previous prime is 21285917. The next prime is 21285941. The reversal of 21285923 is 32958212.

It is a happy number.

It is not a de Polignac number, because 21285923 - 2⁴ = 21285907 is a prime.

It is a super-3 number, since 3×21285923³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21285923.

It is not an unprimeable number, because it can be changed into a prime (21285023) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 11936 + ... + 13602.

It is an arithmetic number, because the mean of its divisors is an integer number (3581474).

Almost surely, 2^21285923 is an apocalyptic number.

21285923 is a deficient number, since it is larger than the sum of its proper divisors (202921).

21285923 is an equidigital number, since it uses as much as digits as its factorization.

21285923 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1893 (or 1780 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 21285923 is about 4613.6669797462. Note that the first 3 decimals coincide. The cubic root of 21285923 is about 277.1389042981.

The spelling of 21285923 in words is "twenty-one million, two hundred eighty-five thousand, nine hundred twenty-three".