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 congruent number.
It is an unprimeable number.
2645120 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).
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 square root of 645120 is about 803.1936254727. The cubic root of 645120 is about 86.4065838604.
Adding to 645120 its reverse (21546), we get a palindrome (666666).
The spelling of 645120 in words is "six hundred forty-five thousand, one hundred twenty".