640605787668 has 720 divisors, whose sum is σ = 2187469734912. Its totient is φ = 159849676800.

The previous prime is 640605787651. The next prime is 640605787709. The reversal of 640605787668 is 866787506046.

It is a super-3 number, since 3×640605787668³ (a number of 36 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 2186367730 + ... + 2186368022.

Almost surely, 2^640605787668 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 640605787668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1093734867456).

640605787668 is an abundant number, since it is smaller than the sum of its proper divisors (1546863947244).

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

640605787668 is a wasteful number, since it uses less digits than its factorization.

640605787668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 626 (or 604 counting only the distinct ones).

The product of its (nonzero) digits is 81285120, while the sum is 63.

The spelling of 640605787668 in words is "six hundred forty billion, six hundred five million, seven hundred eighty-seven thousand, six hundred sixty-eight".