1666989 has 6 divisors (see below), whose sum is σ = 2407886. Its totient is φ = 1111320.

The previous prime is 1666943. The next prime is 1666991. The reversal of 1666989 is 9896661.

It can be written as a sum of positive squares in only one way, i.e., 1550025 + 116964 = 1245^2 + 342^2 .

It is not a de Polignac number, because 1666989 - 2⁸ = 1666733 is a prime.

It is a super-2 number, since 2×1666989² = 5557704652242, 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 (1666909) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 92602 + ... + 92619.

2^1666989 is an apocalyptic number.

It is an amenable number.

1666989 is a deficient number, since it is larger than the sum of its proper divisors (740897).

1666989 is a wasteful number, since it uses less digits than its factorization.

1666989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185227 (or 185224 counting only the distinct ones).

The product of its digits is 139968, while the sum is 45.

The square root of 1666989 is about 1291.1192818636. The cubic root of 1666989 is about 118.5707530255.

The spelling of 1666989 in words is "one million, six hundred sixty-six thousand, nine hundred eighty-nine".