640978853 has 4 divisors (see below), whose sum is σ = 643067040. Its totient is φ = 638890668.

The previous prime is 640978837. The next prime is 640978859. The reversal of 640978853 is 358879046.

640978853 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 a cyclic number.

It is not a de Polignac number, because 640978853 - 2⁴ = 640978837 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 (640978859) 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, 1043633 + ... + 1044246.

It is an arithmetic number, because the mean of its divisors is an integer number (160766760).

Almost surely, 2^640978853 is an apocalyptic number.

It is an amenable number.

640978853 is a deficient number, since it is larger than the sum of its proper divisors (2088187).

640978853 is a wasteful number, since it uses less digits than its factorization.

640978853 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2088186.

The product of its (nonzero) digits is 1451520, while the sum is 50.

The square root of 640978853 is about 25317.5601707590. The cubic root of 640978853 is about 862.2130011434.

The spelling of 640978853 in words is "six hundred forty million, nine hundred seventy-eight thousand, eight hundred fifty-three".