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21665 = 57619
BaseRepresentation
bin101010010100001
31002201102
411102201
51143130
6244145
7120110
oct52241
932642
1021665
1115306
1210655
139b27
147c77
156645
hex54a1

21665 has 8 divisors (see below), whose sum is σ = 29760. Its totient is φ = 14832.

The previous prime is 21661. The next prime is 21673. The reversal of 21665 is 56612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21665 - 22 = 21661 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21661) 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, 275 + ... + 344.

It is an arithmetic number, because the mean of its divisors is an integer number (3720).

221665 is an apocalyptic number.

It is an amenable number.

21665 is a deficient number, since it is larger than the sum of its proper divisors (8095).

21665 is an equidigital number, since it uses as much as digits as its factorization.

21665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 631.

The product of its digits is 360, while the sum is 20.

The square root of 21665 is about 147.1903529447. The cubic root of 21665 is about 27.8774405151.

It can be divided in two parts, 21 and 665, that added together give a palindrome (686).

The spelling of 21665 in words is "twenty-one thousand, six hundred sixty-five".

Divisors: 1 5 7 35 619 3095 4333 21665