21284 has 12 divisors (see below), whose sum is σ = 39564. Its totient is φ = 9984.
The previous prime is 21283. The next prime is 21313. The reversal of 21284 is 48212.
21284 = T17 + T18 + ... + T50.
It can be written as a sum of positive squares in 2 ways, for example, as 6400 + 14884 = 80^2 + 122^2 .
It is a hoax number, since the sum of its digits (17) coincides with the sum of the digits of its distinct prime factors.
It is a Harshad number since it is a multiple of its sum of digits (17).
It is not an unprimeable number, because it can be changed into a prime (21283) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 89 + ... + 224.
It is an arithmetic number, because the mean of its divisors is an integer number (3297).
221284 is an apocalyptic number.
It is an amenable number.
21284 is a deficient number, since it is larger than the sum of its proper divisors (18280).
21284 is a wasteful number, since it uses less digits than its factorization.
21284 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 334 (or 332 counting only the distinct ones).
The product of its digits is 128, while the sum is 17.
The square root of 21284 is about 145.8903697987. The cubic root of 21284 is about 27.7130558342.
Adding to 21284 its product of digits (128), we get a palindrome (21412).
Adding to 21284 its reverse (48212), we get a palindrome (69496).
The spelling of 21284 in words is "twenty-one thousand, two hundred eighty-four".
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