21424320 has 168 divisors, whose sum is σ = 75840336. Its totient is φ = 5548032.

The previous prime is 21424313. The next prime is 21424327. The reversal of 21424320 is 2342412.

It is an interprime number because it is at equal distance from previous prime (21424313) and next prime (21424327).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21424293 and 21424302.

It is not an unprimeable number, because it can be changed into a prime (21424327) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 123754 + ... + 123926.

Almost surely, 2^21424320 is an apocalyptic number.

21424320 is a gapful number since it is divisible by the number (20) 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 21424320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37920168).

21424320 is an abundant number, since it is smaller than the sum of its proper divisors (54416016).

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

21424320 is a wasteful number, since it uses less digits than its factorization.

21424320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 239 (or 226 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21424320 is about 4628.6412693144. The cubic root of 21424320 is about 277.7382419584.

Adding to 21424320 its reverse (2342412), we get a palindrome (23766732).

The spelling of 21424320 in words is "twenty-one million, four hundred twenty-four thousand, three hundred twenty".