1666621 has 8 divisors (see below), whose sum is σ = 1833984. Its totient is φ = 1501920.

The previous prime is 1666619. The next prime is 1666627. The reversal of 1666621 is 1266661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1666621 - 2¹ = 1666619 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1666621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 801 + ... + 1993.

It is an arithmetic number, because the mean of its divisors is an integer number (229248).

2^1666621 is an apocalyptic number.

1666621 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1666621 is a deficient number, since it is larger than the sum of its proper divisors (167363).

1666621 is a wasteful number, since it uses less digits than its factorization.

1666621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1331.

The product of its digits is 2592, while the sum is 28.

The square root of 1666621 is about 1290.9767619907. The cubic root of 1666621 is about 118.5620272634.

The spelling of 1666621 in words is "one million, six hundred sixty-six thousand, six hundred twenty-one".