640807 has 4 divisors (see below), whose sum is σ = 644056. Its totient is φ = 637560.

The previous prime is 640793. The next prime is 640837. The reversal of 640807 is 708046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 708046 = 2 ⋅354023.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640807 is a prime.

It is a super-2 number, since 2×640807² = 821267222498, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1308 + ... + 1729.

It is an arithmetic number, because the mean of its divisors is an integer number (161014).

2⁶⁴⁰⁸⁰⁷ is an apocalyptic number.

640807 is a deficient number, since it is larger than the sum of its proper divisors (3249).

640807 is a wasteful number, since it uses less digits than its factorization.

640807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3248.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 640807 is about 800.5042161038. The cubic root of 640807 is about 86.2135938208.

The spelling of 640807 in words is "six hundred forty thousand, eight hundred seven".