1806661 has 4 divisors (see below), whose sum is σ = 1828512. Its totient is φ = 1784812.

The previous prime is 1806643. The next prime is 1806683. The reversal of 1806661 is 1666081.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1806661 - 2⁷ = 1806533 is a prime.

It is a Duffinian number.

1806661 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1806631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10801 + ... + 10966.

It is an arithmetic number, because the mean of its divisors is an integer number (457128).

2^1806661 is an apocalyptic number.

It is an amenable number.

1806661 is a deficient number, since it is larger than the sum of its proper divisors (21851).

1806661 is an equidigital number, since it uses as much as digits as its factorization.

1806661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21850.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 1806661 is about 1344.1209023001. The cubic root of 1806661 is about 121.7939053773.

The spelling of 1806661 in words is "one million, eight hundred six thousand, six hundred sixty-one".