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20645 = 54129
BaseRepresentation
bin101000010100101
31001022122
411002211
51130040
6235325
7114122
oct50245
931278
1020645
1114569
12bb45
139521
147749
1561b5
hex50a5

20645 has 4 divisors (see below), whose sum is σ = 24780. Its totient is φ = 16512.

The previous prime is 20641. The next prime is 20663. The reversal of 20645 is 54602.

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

It can be written as a sum of positive squares in 2 ways, for example, as 9409 + 11236 = 97^2 + 106^2 .

It is a cyclic number.

It is not a de Polignac number, because 20645 - 22 = 20641 is a prime.

It is a plaindrome in base 11.

It is a nialpdrome in base 13.

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20641) 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, 2060 + ... + 2069.

It is an arithmetic number, because the mean of its divisors is an integer number (6195).

220645 is an apocalyptic number.

It is an amenable number.

20645 is a deficient number, since it is larger than the sum of its proper divisors (4135).

20645 is an equidigital number, since it uses as much as digits as its factorization.

20645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4134.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 20645 is about 143.6836803538. The cubic root of 20645 is about 27.4328942323.

The spelling of 20645 in words is "twenty thousand, six hundred forty-five".

Divisors: 1 5 4129 20645