640656066 has 8 divisors (see below), whose sum is σ = 1281312144. Its totient is φ = 213552020.

The previous prime is 640656061. The next prime is 640656089. The reversal of 640656066 is 660656046.

It is a sphenic number, since it is the product of 3 distinct primes.

640656066 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (640656061) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53388000 + ... + 53388011.

It is an arithmetic number, because the mean of its divisors is an integer number (160164018).

Almost surely, 2^640656066 is an apocalyptic number.

640656066 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

640656066 is a wasteful number, since it uses less digits than its factorization.

640656066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106776016.

The product of its (nonzero) digits is 155520, while the sum is 39.

The square root of 640656066 is about 25311.1846028589. The cubic root of 640656066 is about 862.0682444808.

The spelling of 640656066 in words is "six hundred forty million, six hundred fifty-six thousand, sixty-six".