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21396 = 2231783

21396 has 12 divisors (see below), whose sum is σ = 49952. Its totient is φ = 7128.

The previous prime is 21391. The next prime is 21397. The reversal of 21396 is 69312.

It is a tau number, because it is divible by the number of its divisors (12).

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 21396.

It is not an unprimeable number, because it can be changed into a prime (21391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 880 + ... + 903.

221396 is an apocalyptic number.

It is an amenable number.

21396 is an abundant number, since it is smaller than the sum of its proper divisors (28556).

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 (24976).

21396 is a wasteful number, since it uses less digits than its factorization.

21396 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1790 (or 1788 counting only the distinct ones).

The product of its digits is 324, while the sum is 21.

The square root of 21396 is about 146.2737160258. The cubic root of 21396 is about 27.7615810764.

It can be divided in two parts, 2139 and 6, that added together give a triangular number (2145 = T65).

The spelling of 21396 in words is "twenty-one thousand, three hundred ninety-six".

Divisors: 1 2 3 4 6 12 1783 3566 5349 7132 10698 21396