21544720 has 40 divisors (see below), whose sum is σ = 51264576. Its totient is φ = 8416128.

The previous prime is 21544673. The next prime is 21544723. The reversal of 21544720 is 2744512.

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (21544723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 309 + ... + 6571.

Almost surely, 2^21544720 is an apocalyptic number.

21544720 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 21544720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25632288).

21544720 is an abundant number, since it is smaller than the sum of its proper divisors (29719856).

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

21544720 is a wasteful number, since it uses less digits than its factorization.

21544720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6319 (or 6313 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 25.

The square root of 21544720 is about 4641.6290243836. The cubic root of 21544720 is about 278.2575464673.

The spelling of 21544720 in words is "twenty-one million, five hundred forty-four thousand, seven hundred twenty".