640500538 has 4 divisors (see below), whose sum is σ = 960750810. Its totient is φ = 320250268.

The previous prime is 640500533. The next prime is 640500541. The reversal of 640500538 is 835005046.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 486070209 + 154430329 = 22047^2 + 12427^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (640500533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160125133 + ... + 160125136.

Almost surely, 2^640500538 is an apocalyptic number.

640500538 is a deficient number, since it is larger than the sum of its proper divisors (320250272).

640500538 is a wasteful number, since it uses less digits than its factorization.

640500538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320250271.

The product of its (nonzero) digits is 14400, while the sum is 31.

The square root of 640500538 is about 25308.1120986928. The cubic root of 640500538 is about 861.9984792260.

The spelling of 640500538 in words is "six hundred forty million, five hundred thousand, five hundred thirty-eight".