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12781 is a prime number
BaseRepresentation
bin11000111101101
3122112101
43013231
5402111
6135101
752156
oct30755
918471
1012781
11966a
127491
135a82
14492d
153bc1
hex31ed

12781 has 2 divisors, whose sum is σ = 12782. Its totient is φ = 12780.

The previous prime is 12763. The next prime is 12791. The reversal of 12781 is 18721.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11881 + 900 = 109^2 + 30^2 .

It is a cyclic number.

It is not a de Polignac number, because 12781 - 27 = 12653 is a prime.

It is a super-2 number, since 2×127812 = 326707922, which contains 22 as substring.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

12781 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6390 + 6391.

It is an arithmetic number, because the mean of its divisors is an integer number (6391).

212781 is an apocalyptic number.

12781 is the 72-nd centered pentagonal number.

It is an amenable number.

12781 is a deficient number, since it is larger than the sum of its proper divisors (1).

12781 is an equidigital number, since it uses as much as digits as its factorization.

12781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 112, while the sum is 19.

The square root of 12781 is about 113.0530848761. The cubic root of 12781 is about 23.3805619373.

The spelling of 12781 in words is "twelve thousand, seven hundred eighty-one".