21308424 has 64 divisors (see below), whose sum is σ = 56851200. Its totient is φ = 6636096.

The previous prime is 21308393. The next prime is 21308431. The reversal of 21308424 is 42480312.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a junction number, because it is equal to n+sod(n) for n = 21308394 and 21308403.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37567 + ... + 38129.

It is an arithmetic number, because the mean of its divisors is an integer number (888300).

Almost surely, 2^21308424 is an apocalyptic number.

21308424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21308424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28425600).

21308424 is an abundant number, since it is smaller than the sum of its proper divisors (35542776).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21308424 is a wasteful number, since it uses less digits than its factorization.

21308424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 674 (or 670 counting only the distinct ones).

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

The square root of 21308424 is about 4616.1048514955. The cubic root of 21308424 is about 277.2365229056.

Adding to 21308424 its reverse (42480312), we get a palindrome (63788736).

The spelling of 21308424 in words is "twenty-one million, three hundred eight thousand, four hundred twenty-four".