21725280 has 192 divisors, whose sum is σ = 78382080. Its totient is φ = 5617152.

The previous prime is 21725279. The next prime is 21725293. The reversal of 21725280 is 8252712.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 202987 + ... + 203093.

It is an arithmetic number, because the mean of its divisors is an integer number (408240).

Almost surely, 2^21725280 is an apocalyptic number.

21725280 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 21725280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39191040).

21725280 is an abundant number, since it is smaller than the sum of its proper divisors (56656800).

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

21725280 is a wasteful number, since it uses less digits than its factorization.

21725280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178 (or 164 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21725280 is about 4661.0385108900. The cubic root of 21725280 is about 279.0327167091.

Adding to 21725280 its reverse (8252712), we get a palindrome (29977992).

The spelling of 21725280 in words is "twenty-one million, seven hundred twenty-five thousand, two hundred eighty".