1666221 has 16 divisors (see below), whose sum is σ = 2418624. Its totient is φ = 1016064.

The previous prime is 1666213. The next prime is 1666237. The reversal of 1666221 is 1226661.

It is not a de Polignac number, because 1666221 - 2³ = 1666213 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1666191 and 1666200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666201) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1446 + ... + 2328.

It is an arithmetic number, because the mean of its divisors is an integer number (151164).

2^1666221 is an apocalyptic number.

It is an amenable number.

1666221 is a deficient number, since it is larger than the sum of its proper divisors (752403).

1666221 is a wasteful number, since it uses less digits than its factorization.

1666221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 940.

The product of its digits is 864, while the sum is 24.

The square root of 1666221 is about 1290.8218312378. The cubic root of 1666221 is about 118.5525412824.

The spelling of 1666221 in words is "one million, six hundred sixty-six thousand, two hundred twenty-one".