640351 has 4 divisors (see below), whose sum is σ = 646672. Its totient is φ = 634032.

The previous prime is 640333. The next prime is 640363. The reversal of 640351 is 153046.

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

It is a cyclic number.

It is not a de Polignac number, because 640351 - 2⁷ = 640223 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 (640151) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3006 + ... + 3211.

It is an arithmetic number, because the mean of its divisors is an integer number (161668).

2⁶⁴⁰³⁵¹ is an apocalyptic number.

640351 is a deficient number, since it is larger than the sum of its proper divisors (6321).

640351 is a wasteful number, since it uses less digits than its factorization.

640351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6320.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 640351 is about 800.2193449299. The cubic root of 640351 is about 86.1931390257.

Adding to 640351 its reverse (153046), we get a palindrome (793397).

The spelling of 640351 in words is "six hundred forty thousand, three hundred fifty-one".