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BaseRepresentation
bin1111010101
31100100
433111
512411
64313
72601
oct1725
91310
10981
11812
12699
135a6
14501
15456
hex3d5

981 has 6 divisors (see below), whose sum is σ = 1430. Its totient is φ = 648.

The previous prime is 977. The next prime is 983. The reversal of 981 is 189.

981 is an esthetic number in base 15, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in only one way, i.e., 900 + 81 = 30^2 + 9^2 .

It is not a de Polignac number, because 981 - 22 = 977 is a prime.

It is a super-2 number, since 2×9812 = 1924722, which contains 22 as substring.

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

It is a Duffinian number.

981 is a modest number, since divided by 81 gives 9 as remainder.

981 is a lucky number.

It is a plaindrome in base 12 and base 15.

It is a nialpdrome in base 4 and base 10.

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 (983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 46 + ... + 63.

2981 is an apocalyptic number.

It is an amenable number.

981 is a deficient number, since it is larger than the sum of its proper divisors (449).

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

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

The sum of its prime factors is 115 (or 112 counting only the distinct ones).

The product of its digits is 72, while the sum is 18.

The square root of 981 is about 31.3209195267. The cubic root of 981 is about 9.9362612672.

Adding to 981 its sum of digits (18), we get a palindrome (999).

Subtracting from 981 its product of digits (72), we obtain a palindrome (909).

It can be divided in two parts, 98 and 1, that added together give a palindrome (99).

The spelling of 981 in words is "nine hundred eighty-one", and thus it is an aban number.

Divisors: 1 3 9 109 327 981