21428 has 12 divisors (see below), whose sum is σ = 40992.
Its totient is φ = 9720.
The previous prime is 21419. The next prime is 21433. The reversal of 21428 is 82412.
It is an Ulam number.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21428.
It is an unprimeable number.
21428 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 200 + ... + 287.
It is an arithmetic number, because the mean of its divisors is an integer number (3416).
221428 is an apocalyptic number.
It is an amenable number.
21428 is a deficient number, since it is larger than the sum of its proper divisors (19564).
21428 is a wasteful number, since it uses less digits than its factorization.
21428 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 502 (or 500 counting only the distinct ones).
The product of its digits is 128, while the sum is 17.
The square root of 21428 is about 146.3830591291.
The cubic root of 21428 is about 27.7754143174.
It can be divided in two parts, 214 and 28, that added together give a palindrome (242).
The spelling of 21428 in words is "twenty-one thousand, four hundred twenty-eight".