1664686388 has 12 divisors (see below), whose sum is σ = 2991936612. Its totient is φ = 809847360.

The previous prime is 1664686369. The next prime is 1664686421. The reversal of 1664686388 is 8836864661.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 979189264 + 685497124 = 31292^2 + 26182^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5623793 + ... + 5624088.

It is an arithmetic number, because the mean of its divisors is an integer number (249328051).

Almost surely, 2^1664686388 is an apocalyptic number.

It is an amenable number.

1664686388 is a deficient number, since it is larger than the sum of its proper divisors (1327250224).

1664686388 is a wasteful number, since it uses less digits than its factorization.

1664686388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11247922 (or 11247920 counting only the distinct ones).

The product of its digits is 7962624, while the sum is 56.

The square root of 1664686388 is about 40800.5684764318. The cubic root of 1664686388 is about 1185.1613394002.

The spelling of 1664686388 in words is "one billion, six hundred sixty-four million, six hundred eighty-six thousand, three hundred eighty-eight".