1666685917 has 8 divisors (see below), whose sum is σ = 1796994080. Its totient is φ = 1536678000.

The previous prime is 1666685873. The next prime is 1666685927. The reversal of 1666685917 is 7195866661.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1666685917 - 2⁷ = 1666685789 is a prime.

It is a super-2 number, since 2×1666685917² = 5555683891852261778, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666685927) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 63459 + ... + 85792.

It is an arithmetic number, because the mean of its divisors is an integer number (224624260).

Almost surely, 2^1666685917 is an apocalyptic number.

It is an amenable number.

1666685917 is a deficient number, since it is larger than the sum of its proper divisors (130308163).

1666685917 is a wasteful number, since it uses less digits than its factorization.

1666685917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150123.

The product of its digits is 3265920, while the sum is 55.

The square root of 1666685917 is about 40825.0648131757. The cubic root of 1666685917 is about 1185.6356662379.

The spelling of 1666685917 in words is "one billion, six hundred sixty-six million, six hundred eighty-five thousand, nine hundred seventeen".