21281280 has 160 divisors (see below), whose sum is σ = 72477504. Its totient is φ = 5308416.

The previous prime is 21281261. The next prime is 21281321. The reversal of 21281280 is 8218212.

It is a tau number, because it is divible by the number of its divisors (160).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21281280.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 130479 + ... + 130641.

Almost surely, 2^21281280 is an apocalyptic number.

21281280 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 21281280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36238752).

21281280 is an abundant number, since it is smaller than the sum of its proper divisors (51196224).

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

21281280 is a wasteful number, since it uses less digits than its factorization.

21281280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 190 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 24.

The square root of 21281280 is about 4613.1637733772. The cubic root of 21281280 is about 277.1187524901.

Adding to 21281280 its reverse (8218212), we get a palindrome (29499492).

The spelling of 21281280 in words is "twenty-one million, two hundred eighty-one thousand, two hundred eighty".