640040220 has 36 divisors (see below), whose sum is σ = 1941455880. Its totient is φ = 170677344.

The previous prime is 640040197. The next prime is 640040231. The reversal of 640040220 is 22040046.

640040220 is a `hidden beast` number, since 6 + 400 + 40 + 220 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

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 = 640040193 and 640040202.

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, 1777710 + ... + 1778069.

It is an arithmetic number, because the mean of its divisors is an integer number (53929330).

Almost surely, 2^640040220 is an apocalyptic number.

640040220 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640040220 is an abundant number, since it is smaller than the sum of its proper divisors (1301415660).

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

640040220 is a wasteful number, since it uses less digits than its factorization.

640040220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3555794 (or 3555789 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 640040220 is about 25299.0161864054. The cubic root of 640040220 is about 861.7919280019.

Adding to 640040220 its reverse (22040046), we get a palindrome (662080266).

The spelling of 640040220 in words is "six hundred forty million, forty thousand, two hundred twenty".