21376 has 16 divisors (see below), whose sum is σ = 42840. Its totient is φ = 10624.
The previous prime is 21347. The next prime is 21377. The reversal of 21376 is 67312.
It is a tau number, because it is divible by the number of its divisors (16).
It is a nialpdrome in base 13.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (21377) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45 + ... + 211.
221376 is an apocalyptic number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 21376, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21420).
21376 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21376 is an equidigital number, since it uses as much as digits as its factorization.
21376 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 181 (or 169 counting only the distinct ones).
The product of its digits is 252, while the sum is 19.
The square root of 21376 is about 146.2053350600. The cubic root of 21376 is about 27.7529282953.
Adding to 21376 its reverse (67312), we get a palindrome (88688).
It can be divided in two parts, 213 and 76, that added together give a square (289 = 172).
The spelling of 21376 in words is "twenty-one thousand, three hundred seventy-six".
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