664981671 has 4 divisors (see below), whose sum is σ = 886642232. Its totient is φ = 443321112.

The previous prime is 664981643. The next prime is 664981729. The reversal of 664981671 is 176189466.

It is a happy number.

664981671 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.

It is not a de Polignac number, because 664981671 - 2²⁵ = 631427239 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 664981671.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664980671) 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, 110830276 + ... + 110830281.

It is an arithmetic number, because the mean of its divisors is an integer number (221660558).

Almost surely, 2^664981671 is an apocalyptic number.

664981671 is a deficient number, since it is larger than the sum of its proper divisors (221660561).

664981671 is a wasteful number, since it uses less digits than its factorization.

664981671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221660560.

The product of its digits is 435456, while the sum is 48.

The square root of 664981671 is about 25787.2385299396. The cubic root of 664981671 is about 872.8438541457.

The spelling of 664981671 in words is "six hundred sixty-four million, nine hundred eighty-one thousand, six hundred seventy-one".