21424040 has 128 divisors (see below), whose sum is σ = 57542400. Its totient is φ = 7096320.

The previous prime is 21424027. The next prime is 21424049. The reversal of 21424040 is 4042412.

It is not an unprimeable number, because it can be changed into a prime (21424049) 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 in 31 ways as a sum of consecutive naturals, for example, 293444 + ... + 293516.

It is an arithmetic number, because the mean of its divisors is an integer number (449550).

Almost surely, 2^21424040 is an apocalyptic number.

21424040 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 21424040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28771200).

21424040 is an abundant number, since it is smaller than the sum of its proper divisors (36118360).

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

21424040 is a wasteful number, since it uses less digits than its factorization.

21424040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 147 (or 143 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 21424040 is about 4628.6110227583. The cubic root of 21424040 is about 277.7370320087.

Adding to 21424040 its reverse (4042412), we get a palindrome (25466452).

The spelling of 21424040 in words is "twenty-one million, four hundred twenty-four thousand, forty".