640509768 has 160 divisors (see below), whose sum is σ = 1860418560. Its totient is φ = 205752960.

The previous prime is 640509767. The next prime is 640509769. The reversal of 640509768 is 867905046.

It is an interprime number because it is at equal distance from previous prime (640509767) and next prime (640509769).

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (640509761) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 3538638 + ... + 3538818.

It is an arithmetic number, because the mean of its divisors is an integer number (11627616).

Almost surely, 2^640509768 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 640509768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (930209280).

640509768 is an abundant number, since it is smaller than the sum of its proper divisors (1219908792).

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

640509768 is a wasteful number, since it uses less digits than its factorization.

640509768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 369 (or 356 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 45.

The square root of 640509768 is about 25308.2944506342. The cubic root of 640509768 is about 862.0026198459.

The spelling of 640509768 in words is "six hundred forty million, five hundred nine thousand, seven hundred sixty-eight".