640765806 has 16 divisors (see below), whose sum is σ = 1284595200. Its totient is φ = 213078008.

The previous prime is 640765799. The next prime is 640765831. The reversal of 640765806 is 608567046.

It is a happy number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 124926 + ... + 129953.

It is an arithmetic number, because the mean of its divisors is an integer number (80287200).

Almost surely, 2^640765806 is an apocalyptic number.

640765806 is an abundant number, since it is smaller than the sum of its proper divisors (643829394).

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

640765806 is a wasteful number, since it uses less digits than its factorization.

640765806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255303.

The product of its (nonzero) digits is 241920, while the sum is 42.

The square root of 640765806 is about 25313.3523263909. The cubic root of 640765806 is about 862.1174638009.

The spelling of 640765806 in words is "six hundred forty million, seven hundred sixty-five thousand, eight hundred six".