640711816 has 8 divisors (see below), whose sum is σ = 1201334670. Its totient is φ = 320355904.

The previous prime is 640711811. The next prime is 640711817. The reversal of 640711816 is 618117046.

It can be written as a sum of positive squares in only one way, i.e., 568631716 + 72080100 = 23846^2 + 8490^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (640711811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40044481 + ... + 40044496.

Almost surely, 2^640711816 is an apocalyptic number.

It is an amenable number.

640711816 is a deficient number, since it is larger than the sum of its proper divisors (560622854).

640711816 is a wasteful number, since it uses less digits than its factorization.

640711816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80088983 (or 80088979 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 34.

The square root of 640711816 is about 25312.2858706992. The cubic root of 640711816 is about 862.0932495306.

The spelling of 640711816 in words is "six hundred forty million, seven hundred eleven thousand, eight hundred sixteen".