640242640 has 20 divisors (see below), whose sum is σ = 1488564324. Its totient is φ = 256097024.

The previous prime is 640242637. The next prime is 640242653. The reversal of 640242640 is 46242046.

It can be written as a sum of positive squares in 2 ways, for example, as 345365056 + 294877584 = 18584^2 + 17172^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 640242599 and 640242608.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4001437 + ... + 4001596.

Almost surely, 2^640242640 is an apocalyptic number.

It is an amenable number.

640242640 is an abundant number, since it is smaller than the sum of its proper divisors (848321684).

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

640242640 is a wasteful number, since it uses less digits than its factorization.

640242640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8003046 (or 8003040 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 28.

The square root of 640242640 is about 25303.0164209724. The cubic root of 640242640 is about 861.8827689262.

Adding to 640242640 its reverse (46242046), we get a palindrome (686484686).

The spelling of 640242640 in words is "six hundred forty million, two hundred forty-two thousand, six hundred forty".