640671357 has 4 divisors (see below), whose sum is σ = 854228480. Its totient is φ = 427114236.

The previous prime is 640671329. The next prime is 640671359. The reversal of 640671357 is 753176046.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 640671357 - 2²⁸ = 372235901 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 (640671359) 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, 106778557 + ... + 106778562.

It is an arithmetic number, because the mean of its divisors is an integer number (213557120).

Almost surely, 2^640671357 is an apocalyptic number.

It is an amenable number.

640671357 is a deficient number, since it is larger than the sum of its proper divisors (213557123).

640671357 is a wasteful number, since it uses less digits than its factorization.

640671357 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213557122.

The product of its (nonzero) digits is 105840, while the sum is 39.

The square root of 640671357 is about 25311.4866611979. The cubic root of 640671357 is about 862.0751029609.

The spelling of 640671357 in words is "six hundred forty million, six hundred seventy-one thousand, three hundred fifty-seven".