99840 has 80 divisors (see below), whose sum is σ = 343728. Its totient is φ = 24576.

The previous prime is 99839. The next prime is 99859. The reversal of 99840 is 4899.

It can be divided in two parts, 99 and 840, that added together give a palindrome (939).

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

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a nialpdrome in base 10.

It is a zygodrome in base 2.

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 99798 and 99807.

It is a congruent number.

It is an inconsummate number, since it does not exist a number *n* which divided by its sum of digits gives 99840.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7674 + ... + 7686.

2^{99840} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 99840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (171864).

99840 is an abundant number, since it is smaller than the sum of its proper divisors (243888).

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

99840 is a wasteful number, since it uses less digits than its factorization.

99840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39 (or 23 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 99840 is about 315.9746825301. The cubic root of 99840 is about 46.3911199812.

The spelling of 99840 in words is "ninety-nine thousand, eight hundred forty".

Divisors: 1 2 3 4 5 6 8 10 12 13 15 16 20 24 26 30 32 39 40 48 52 60 64 65 78 80 96 104 120 128 130 156 160 192 195 208 240 256 260 312 320 384 390 416 480 512 520 624 640 768 780 832 960 1040 1248 1280 1536 1560 1664 1920 2080 2496 2560 3120 3328 3840 4160 4992 6240 6656 7680 8320 9984 12480 16640 19968 24960 33280 49920 99840

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