21745880 has 128 divisors (see below), whose sum is σ = 58060800. Its totient is φ = 7257600.

The previous prime is 21745799. The next prime is 21745901. The reversal of 21745880 is 8854712.

It is a self number, because there is not a number n which added to its sum of digits gives 21745880.

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, 306245 + ... + 306315.

It is an arithmetic number, because the mean of its divisors is an integer number (453600).

Almost surely, 2^21745880 is an apocalyptic number.

21745880 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 21745880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29030400).

21745880 is an abundant number, since it is smaller than the sum of its proper divisors (36314920).

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

21745880 is a wasteful number, since it uses less digits than its factorization.

21745880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145 (or 141 counting only the distinct ones).

The product of its (nonzero) digits is 17920, while the sum is 35.

The square root of 21745880 is about 4663.2477952603. The cubic root of 21745880 is about 279.1208821725.

The spelling of 21745880 in words is "twenty-one million, seven hundred forty-five thousand, eight hundred eighty".