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21971 = 127173
BaseRepresentation
bin101010111010011
31010010202
411113103
51200341
6245415
7121025
oct52723
933122
1021971
1115564
121086b
13a001
148015
15679b
hex55d3

21971 has 4 divisors (see below), whose sum is σ = 22272. Its totient is φ = 21672.

The previous prime is 21961. The next prime is 21977. The reversal of 21971 is 17912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21971 - 210 = 20947 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (21977) 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, 41 + ... + 213.

It is an arithmetic number, because the mean of its divisors is an integer number (5568).

221971 is an apocalyptic number.

21971 is a deficient number, since it is larger than the sum of its proper divisors (301).

21971 is a wasteful number, since it uses less digits than its factorization.

21971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 300.

The product of its digits is 126, while the sum is 20.

The square root of 21971 is about 148.2261785246. The cubic root of 21971 is about 28.0080759018.

The spelling of 21971 in words is "twenty-one thousand, nine hundred seventy-one".

Divisors: 1 127 173 21971