21985280 has 96 divisors (see below), whose sum is σ = 56019600. Its totient is φ = 8257536.

The previous prime is 21985279. The next prime is 21985283. The reversal of 21985280 is 8258912.

It is a self number, because there is not a number n which added to its sum of digits gives 21985280.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21985283) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 194504 + ... + 194616.

Almost surely, 2^21985280 is an apocalyptic number.

21985280 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 21985280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28009800).

21985280 is an abundant number, since it is smaller than the sum of its proper divisors (34034320).

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

21985280 is a wasteful number, since it uses less digits than its factorization.

21985280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159 (or 139 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 21985280 is about 4688.8463399860. The cubic root of 21985280 is about 280.1414251542.

The spelling of 21985280 in words is "twenty-one million, nine hundred eighty-five thousand, two hundred eighty".