1664886661 has 4 divisors (see below), whose sum is σ = 1666161792. Its totient is φ = 1663611532.

The previous prime is 1664886659. The next prime is 1664886673. The reversal of 1664886661 is 1666884661.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1666884661 = 13 ⋅128221897.

It is a cyclic number.

It is not a de Polignac number, because 1664886661 - 2¹ = 1664886659 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1664886599 and 1664886608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1664880661) 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, 635605 + ... + 638218.

It is an arithmetic number, because the mean of its divisors is an integer number (416540448).

Almost surely, 2^1664886661 is an apocalyptic number.

It is an amenable number.

1664886661 is a deficient number, since it is larger than the sum of its proper divisors (1275131).

1664886661 is a wasteful number, since it uses less digits than its factorization.

1664886661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1275130.

The product of its digits is 1990656, while the sum is 52.

The square root of 1664886661 is about 40803.0226944034. The cubic root of 1664886661 is about 1185.2088651285.

The spelling of 1664886661 in words is "one billion, six hundred sixty-four million, eight hundred eighty-six thousand, six hundred sixty-one".