640256631066 has 128 divisors (see below), whose sum is σ = 1539880554240. Its totient is φ = 196021223424.

The previous prime is 640256631023. The next prime is 640256631109. The reversal of 640256631066 is 660136652046.

640256631066 is a `hidden beast` number, since 6 + 4 + 0 + 2 + 5 + 6 + 631 + 0 + 6 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (640256631023) and next prime (640256631109).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 267552766 + ... + 267555158.

It is an arithmetic number, because the mean of its divisors is an integer number (12030316830).

Almost surely, 2^640256631066 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640256631066, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (769940277120).

640256631066 is an abundant number, since it is smaller than the sum of its proper divisors (899623923174).

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

640256631066 is a wasteful number, since it uses less digits than its factorization.

640256631066 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4157 (or 4151 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 45.

The spelling of 640256631066 in words is "six hundred forty billion, two hundred fifty-six million, six hundred thirty-one thousand, sixty-six".