640640000 has 440 divisors, whose sum is σ = 2148662208. Its totient is φ = 184320000.

The previous prime is 640639981. The next prime is 640640003. The reversal of 640640000 is 46046.

It is a tau number, because it is divible by the number of its divisors (440).

It is a hoax number, since the sum of its digits (20) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is not an unprimeable number, because it can be changed into a prime (640640003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 49279994 + ... + 49280006.

Almost surely, 2^640640000 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640640000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1074331104).

640640000 is an abundant number, since it is smaller than the sum of its proper divisors (1508022208).

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

640640000 is a wasteful number, since it uses less digits than its factorization.

640640000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71 (or 38 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 640640000 is about 25310.8672312902. The cubic root of 640640000 is about 862.0610382719.

Adding to 640640000 its reverse (46046), we get a palindrome (640686046).

The spelling of 640640000 in words is "six hundred forty million, six hundred forty thousand".