2191666 has 4 divisors (see below), whose sum is σ = 3287502. Its totient is φ = 1095832.

The previous prime is 2191633. The next prime is 2191687. The reversal of 2191666 is 6661912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 2187441 + 4225 = 1479^2 + 65^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 547915 + ... + 547918.

2^2191666 is an apocalyptic number.

2191666 is a deficient number, since it is larger than the sum of its proper divisors (1095836).

2191666 is a wasteful number, since it uses less digits than its factorization.

2191666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1095835.

The product of its digits is 3888, while the sum is 31.

The square root of 2191666 is about 1480.4276409200. The cubic root of 2191666 is about 129.8947076418.

The spelling of 2191666 in words is "two million, one hundred ninety-one thousand, six hundred sixty-six".