21240024 has 64 divisors (see below), whose sum is σ = 60211200. Its totient is φ = 6189696.

The previous prime is 21240001. The next prime is 21240049. The reversal of 21240024 is 42004212.

It is a super-2 number, since 2×21240024² = 902277239041152, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21239985 and 21240012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4137 + ... + 7719.

It is an arithmetic number, because the mean of its divisors is an integer number (940800).

Almost surely, 2^21240024 is an apocalyptic number.

21240024 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 21240024, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30105600).

21240024 is an abundant number, since it is smaller than the sum of its proper divisors (38971176).

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

21240024 is a wasteful number, since it uses less digits than its factorization.

21240024 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3624 (or 3620 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21240024 is about 4608.6900524986. The cubic root of 21240024 is about 276.9395620291.

Adding to 21240024 its reverse (42004212), we get a palindrome (63244236).

The spelling of 21240024 in words is "twenty-one million, two hundred forty thousand, twenty-four".