21724080 has 160 divisors (see below), whose sum is σ = 78518784. Its totient is φ = 4866048.

The previous prime is 21724057. The next prime is 21724081. The reversal of 21724080 is 8042712.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21724080.

It is not an unprimeable number, because it can be changed into a prime (21724081) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 112464 + ... + 112656.

Almost surely, 2^21724080 is an apocalyptic number.

21724080 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 21724080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39259392).

21724080 is an abundant number, since it is smaller than the sum of its proper divisors (56794704).

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

21724080 is a wasteful number, since it uses less digits than its factorization.

21724080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 283 (or 277 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21724080 is about 4660.9097824352. The cubic root of 21724080 is about 279.0275791393.

Adding to 21724080 its reverse (8042712), we get a palindrome (29766792).

The spelling of 21724080 in words is "twenty-one million, seven hundred twenty-four thousand, eighty".