1666394 has 4 divisors (see below), whose sum is σ = 2499594. Its totient is φ = 833196.

The previous prime is 1666393. The next prime is 1666397. The reversal of 1666394 is 4936661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 4936661 = 1993 ⋅2477.

It can be written as a sum of positive squares in only one way, i.e., 1452025 + 214369 = 1205^2 + 463^2 .

It is a super-3 number, since 3×1666394³ = 13882073337368072952, which contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (1666393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 416597 + ... + 416600.

2^1666394 is an apocalyptic number.

1666394 is a deficient number, since it is larger than the sum of its proper divisors (833200).

1666394 is an equidigital number, since it uses as much as digits as its factorization.

1666394 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 833199.

The product of its digits is 23328, while the sum is 35.

The square root of 1666394 is about 1290.8888410704. Note that the first 4 decimals coincide. The cubic root of 1666394 is about 118.5566441554.

The spelling of 1666394 in words is "one million, six hundred sixty-six thousand, three hundred ninety-four".