21275280 has 120 divisors (see below), whose sum is σ = 76979448. Its totient is φ = 5234688.

The previous prime is 21275237. The next prime is 21275281. The reversal of 21275280 is 8257212.

It can be written as a sum of positive squares in 4 ways, for example, as 2509056 + 18766224 = 1584^2 + 4332^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is not an unprimeable number, because it can be changed into a prime (21275281) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8224 + ... + 10496.

Almost surely, 2^21275280 is an apocalyptic number.

21275280 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 21275280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38489724).

21275280 is an abundant number, since it is smaller than the sum of its proper divisors (55704168).

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

21275280 is a wasteful number, since it uses less digits than its factorization.

21275280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2305 (or 2296 counting only the distinct ones).

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

The square root of 21275280 is about 4612.5134146146. The cubic root of 21275280 is about 277.0927066131.

The spelling of 21275280 in words is "twenty-one million, two hundred seventy-five thousand, two hundred eighty".