640006397 has 4 divisors (see below), whose sum is σ = 646343196. Its totient is φ = 633669600.

The previous prime is 640006369. The next prime is 640006417. The reversal of 640006397 is 793600046.

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

It can be written as a sum of positive squares in 2 ways, for example, as 619312996 + 20693401 = 24886^2 + 4549^2 .

It is a cyclic number.

It is not a de Polignac number, because 640006397 - 2⁶ = 640006333 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640006357) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3168248 + ... + 3168449.

It is an arithmetic number, because the mean of its divisors is an integer number (161585799).

Almost surely, 2^640006397 is an apocalyptic number.

It is an amenable number.

640006397 is a deficient number, since it is larger than the sum of its proper divisors (6336799).

640006397 is a wasteful number, since it uses less digits than its factorization.

640006397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6336798.

The product of its (nonzero) digits is 27216, while the sum is 35.

The square root of 640006397 is about 25298.3477128448. The cubic root of 640006397 is about 861.7767472363.

The spelling of 640006397 in words is "six hundred forty million, six thousand, three hundred ninety-seven".