640427 has 4 divisors (see below), whose sum is σ = 644520. Its totient is φ = 636336.

The previous prime is 640421. The next prime is 640457. The reversal of 640427 is 724046.

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 640427 - 2⁴ = 640411 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640427.

It is not an unprimeable number, because it can be changed into a prime (640421) 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, 1802 + ... + 2127.

It is an arithmetic number, because the mean of its divisors is an integer number (161130).

2⁶⁴⁰⁴²⁷ is an apocalyptic number.

640427 is a deficient number, since it is larger than the sum of its proper divisors (4093).

640427 is a wasteful number, since it uses less digits than its factorization.

640427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4092.

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 640427 is about 800.2668305009. The cubic root of 640427 is about 86.1965488325.

The spelling of 640427 in words is "six hundred forty thousand, four hundred twenty-seven".