21380 has 12 divisors (see below), whose sum is σ = 44940. Its totient is φ = 8544.

The previous prime is 21379. The next prime is 21383. The reversal of 21380 is 8312.

It can be written as a sum of positive squares in 2 ways, for example, as 8836 + 12544 = 94^2 + 112^2 .

It is not an unprimeable number, because it can be changed into a prime (21383) 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, 515 + ... + 554.

It is an arithmetic number, because the mean of its divisors is an integer number (3745).

2²¹³⁸⁰ is an apocalyptic number.

21380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21380 is an abundant number, since it is smaller than the sum of its proper divisors (23560).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22470).

21380 is a wasteful number, since it uses less digits than its factorization.

21380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1078 (or 1076 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21380 is about 146.2190138115. The cubic root of 21380 is about 27.7546592831.

Adding to 21380 its reverse (8312), we get a palindrome (29692).

The spelling of 21380 in words is "twenty-one thousand, three hundred eighty".