1666486681 has 4 divisors (see below), whose sum is σ = 1667811600. Its totient is φ = 1665161764.

The previous prime is 1666486673. The next prime is 1666486687. The reversal of 1666486681 is 1866846661.

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.

It is a cyclic number.

It is not a de Polignac number, because 1666486681 - 2³ = 1666486673 is a prime.

It is a super-3 number, since 3×1666486681³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666486687) 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, 660571 + ... + 663088.

It is an arithmetic number, because the mean of its divisors is an integer number (416952900).

Almost surely, 2^1666486681 is an apocalyptic number.

It is an amenable number.

1666486681 is a deficient number, since it is larger than the sum of its proper divisors (1324919).

1666486681 is a wasteful number, since it uses less digits than its factorization.

1666486681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1324918.

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

The square root of 1666486681 is about 40822.6246216482. The cubic root of 1666486681 is about 1185.5884206394.

The spelling of 1666486681 in words is "one billion, six hundred sixty-six million, four hundred eighty-six thousand, six hundred eighty-one".