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21138 = 2313271

21138 has 16 divisors (see below), whose sum is σ = 45696. Its totient is φ = 6480.

The previous prime is 21121. The next prime is 21139. The reversal of 21138 is 83112.

It is a happy number.

It is a plaindrome in base 14.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21139) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 58 + ... + 213.

It is an arithmetic number, because the mean of its divisors is an integer number (2856).

221138 is an apocalyptic number.

21138 is an abundant number, since it is smaller than the sum of its proper divisors (24558).

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 (22848).

21138 is a wasteful number, since it uses less digits than its factorization.

21138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289.

The product of its digits is 48, while the sum is 15.

The square root of 21138 is about 145.3891330189. The cubic root of 21138 is about 27.6495434439.

The spelling of 21138 in words is "twenty-one thousand, one hundred thirty-eight".

Divisors: 1 2 3 6 13 26 39 78 271 542 813 1626 3523 7046 10569 21138