640020 has 24 divisors (see below), whose sum is σ = 1792224. Its totient is φ = 170656.

The previous prime is 640019. The next prime is 640027. The reversal of 640020 is 20046.

640020 = T₃₉₆ + T₃₉₇ + ... + T₄₀₃.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 639978 and 640005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640027) 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 7 ways as a sum of consecutive naturals, for example, 5274 + ... + 5393.

It is an arithmetic number, because the mean of its divisors is an integer number (74676).

2⁶⁴⁰⁰²⁰ is an apocalyptic number.

640020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640020 is an abundant number, since it is smaller than the sum of its proper divisors (1152204).

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

640020 is a wasteful number, since it uses less digits than its factorization.

640020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10679 (or 10677 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 12.

The square root of 640020 is about 800.0124999023. The cubic root of 640020 is about 86.1782852730.

640020 divided by its sum of digits (12) gives a palindrome (53335).

Adding to 640020 its reverse (20046), we get a palindrome (660066).

The spelling of 640020 in words is "six hundred forty thousand, twenty".