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81840 = 24351131
BaseRepresentation
bin10011111110110000
311011021010
4103332300
510104330
61430520
7460413
oct237660
9134233
1081840
1156540
123b440
132b335
1421b7a
15193b0
hex13fb0

81840 has 80 divisors (see below), whose sum is σ = 285696. Its totient is φ = 19200.

The previous prime is 81839. The next prime is 81847. The reversal of 81840 is 4818.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81847) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2625 + ... + 2655.

281840 is an apocalyptic number.

81840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (142848).

81840 is an abundant number, since it is smaller than the sum of its proper divisors (203856).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81840 is a wasteful number, since it uses less digits than its factorization.

81840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58 (or 52 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 21.

The square root of 81840 is about 286.0769127350. The cubic root of 81840 is about 43.4165396692.

It can be divided in two parts, 818 and 40, that added together give a palindrome (858).

The spelling of 81840 in words is "eighty-one thousand, eight hundred forty".

Divisors: 1 2 3 4 5 6 8 10 11 12 15 16 20 22 24 30 31 33 40 44 48 55 60 62 66 80 88 93 110 120 124 132 155 165 176 186 220 240 248 264 310 330 341 372 440 465 496 528 620 660 682 744 880 930 1023 1240 1320 1364 1488 1705 1860 2046 2480 2640 2728 3410 3720 4092 5115 5456 6820 7440 8184 10230 13640 16368 20460 27280 40920 81840