640640242 has 16 divisors (see below), whose sum is σ = 1063088064. Its totient is φ = 287098000.

The previous prime is 640640213. The next prime is 640640249. The reversal of 640640242 is 242046046.

It is a self number, because there is not a number n which added to its sum of digits gives 640640242.

It is not an unprimeable number, because it can be changed into a prime (640640249) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 203509 + ... + 206632.

It is an arithmetic number, because the mean of its divisors is an integer number (66443004).

Almost surely, 2^640640242 is an apocalyptic number.

640640242 is a deficient number, since it is larger than the sum of its proper divisors (422447822).

640640242 is a wasteful number, since it uses less digits than its factorization.

640640242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410225.

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

The square root of 640640242 is about 25310.8720118450. The cubic root of 640640242 is about 862.0611468190.

Adding to 640640242 its reverse (242046046), we get a palindrome (882686288).

The spelling of 640640242 in words is "six hundred forty million, six hundred forty thousand, two hundred forty-two".