1665778 has 4 divisors (see below), whose sum is σ = 2498670. Its totient is φ = 832888.

The previous prime is 1665767. The next prime is 1665823. The reversal of 1665778 is 8775661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8775661 = 29 ⋅302609.

It can be written as a sum of positive squares in only one way, i.e., 1656369 + 9409 = 1287^2 + 97^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 1665778.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 416443 + ... + 416446.

2^1665778 is an apocalyptic number.

1665778 is a deficient number, since it is larger than the sum of its proper divisors (832892).

1665778 is an equidigital number, since it uses as much as digits as its factorization.

1665778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 832891.

The product of its digits is 70560, while the sum is 40.

The square root of 1665778 is about 1290.6502237245. The cubic root of 1665778 is about 118.5420337865.

The spelling of 1665778 in words is "one million, six hundred sixty-five thousand, seven hundred seventy-eight".