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21671 = 131667
BaseRepresentation
bin101010010100111
31002201122
411102213
51143141
6244155
7120116
oct52247
932648
1021671
1115311
121065b
139b30
147c7d
15664b
hex54a7

21671 has 4 divisors (see below), whose sum is σ = 23352. Its totient is φ = 19992.

The previous prime is 21661. The next prime is 21673. The reversal of 21671 is 17612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2k-21671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21673) 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, 821 + ... + 846.

It is an arithmetic number, because the mean of its divisors is an integer number (5838).

221671 is an apocalyptic number.

21671 is a deficient number, since it is larger than the sum of its proper divisors (1681).

21671 is a wasteful number, since it uses less digits than its factorization.

21671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1680.

The product of its digits is 84, while the sum is 17.

The square root of 21671 is about 147.2107333043. The cubic root of 21671 is about 27.8800137777.

The spelling of 21671 in words is "twenty-one thousand, six hundred seventy-one".

Divisors: 1 13 1667 21671