640640385 has 192 divisors, whose sum is σ = 1502392320. Its totient is φ = 244477440.

The previous prime is 640640381. The next prime is 640640411. The reversal of 640640385 is 583046046.

640640385 is a `hidden beast` number, since 6 + 4 + 0 + 640 + 3 + 8 + 5 = 666.

It is not a de Polignac number, because 640640385 - 2² = 640640381 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640640381) by changing a digit.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 2435764 + ... + 2436026.

It is an arithmetic number, because the mean of its divisors is an integer number (7824960).

Almost surely, 2^640640385 is an apocalyptic number.

It is an amenable number.

640640385 is an abundant number, since it is smaller than the sum of its proper divisors (861751935).

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

640640385 is a wasteful number, since it uses less digits than its factorization.

640640385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 348 (or 345 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The square root of 640640385 is about 25310.8748367179. The cubic root of 640640385 is about 862.0612109604.

The spelling of 640640385 in words is "six hundred forty million, six hundred forty thousand, three hundred eighty-five".