645120 has 144 divisors (see below), whose sum is σ = 2555280. Its totient is φ = 147456.

The previous prime is 645097. The next prime is 645131. The reversal of 645120 is 21546.

Adding to 645120 its reverse (21546), we get a palindrome (666666).

It can be divided in two parts, 64 and 5120, that added together give a square (5184 = 72^{2}).

It is a happy number.

It is a Jordan-Polya number, since it can be written as 8! ⋅ (2!)^{4}.

It is a double factorial (645120 = 14 !! = 2 ⋅ 4 ⋅ 6 ⋅ 8 ⋅ 10 ⋅ 12 ⋅ 14 ).

645120 is a *`hidden beast`* number, since 645 + 1 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 645093 and 645102.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 92157 + ... + 92163.

It is an arithmetic number, because the mean of its divisors is an integer number (17745).

2^{645120} is an apocalyptic number.

645120 is a gapful number since it is divisible by the number (60) 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 645120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1277640).

645120 is an abundant number, since it is smaller than the sum of its proper divisors (1910160).

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

645120 is a wasteful number, since it uses less digits than its factorization.

645120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40 (or 17 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 645120 is about 803.1936254727. The cubic root of 645120 is about 86.4065838604.

The spelling of 645120 in words is "six hundred forty-five thousand, one hundred twenty".

Divisors: 1 2 3 4 5 6 7 8 9 10 12 14 15 16 18 20 21 24 28 30 32 35 36 40 42 45 48 56 60 63 64 70 72 80 84 90 96 105 112 120 126 128 140 144 160 168 180 192 210 224 240 252 256 280 288 315 320 336 360 384 420 448 480 504 512 560 576 630 640 672 720 768 840 896 960 1008 1024 1120 1152 1260 1280 1344 1440 1536 1680 1792 1920 2016 2048 2240 2304 2520 2560 2688 2880 3072 3360 3584 3840 4032 4480 4608 5040 5120 5376 5760 6144 6720 7168 7680 8064 8960 9216 10080 10240 10752 11520 13440 14336 15360 16128 17920 18432 20160 21504 23040 26880 30720 32256 35840 40320 43008 46080 53760 64512 71680 80640 92160 107520 129024 161280 215040 322560 645120

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