21281288 has 36 divisors (see below), whose sum is σ = 46617165. Its totient is φ = 9081408.

The previous prime is 21281261. The next prime is 21281321. The reversal of 21281288 is 88218212.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 2 ways, for example, as 19201924 + 2079364 = 4382^2 + 1442^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3262.

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 91220 + ... + 91452.

Almost surely, 2^21281288 is an apocalyptic number.

21281288 is a gapful number since it is divisible by the number (28) 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 21281288

21281288 is an abundant number, since it is smaller than the sum of its proper divisors (25335877).

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

21281288 is an equidigital number, since it uses as much as digits as its factorization.

21281288 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 486 (or 242 counting only the distinct ones).

The product of its digits is 4096, while the sum is 32.

The square root of 21281288 is about 4613.1646404610. The cubic root of 21281288 is about 277.1187872147.

Multiplying 21281288 by its sum of digits (32), we get a square (681001216 = 26096²).

The spelling of 21281288 in words is "twenty-one million, two hundred eighty-one thousand, two hundred eighty-eight".