21242823 has 48 divisors (see below), whose sum is σ = 35283456. Its totient is φ = 11309760.

The previous prime is 21242821. The next prime is 21242827. The reversal of 21242823 is 32824212.

It is not a de Polignac number, because 21242823 - 2¹ = 21242821 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21242793 and 21242802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21242821) 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 47 ways as a sum of consecutive naturals, for example, 206190 + ... + 206292.

It is an arithmetic number, because the mean of its divisors is an integer number (735072).

Almost surely, 2^21242823 is an apocalyptic number.

21242823 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21242823 is a deficient number, since it is larger than the sum of its proper divisors (14040633).

21242823 is a wasteful number, since it uses less digits than its factorization.

21242823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204 (or 197 counting only the distinct ones).

The product of its digits is 1536, while the sum is 24.

The square root of 21242823 is about 4608.9937079584. The cubic root of 21242823 is about 276.9517264815.

The spelling of 21242823 in words is "twenty-one million, two hundred forty-two thousand, eight hundred twenty-three".