1663661 has 4 divisors (see below), whose sum is σ = 1684800. Its totient is φ = 1642524.

The previous prime is 1663619. The next prime is 1663681.

1663661 is nontrivially palindromic in base 10.

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 1663661 - 2¹⁰ = 1662637 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1663681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10451 + ... + 10608.

It is an arithmetic number, because the mean of its divisors is an integer number (421200).

2^1663661 is an apocalyptic number.

It is an amenable number.

1663661 is a deficient number, since it is larger than the sum of its proper divisors (21139).

1663661 is an equidigital number, since it uses as much as digits as its factorization.

1663661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21138.

The product of its digits is 3888, while the sum is 29.

The square root of 1663661 is about 1289.8298337378. The cubic root of 1663661 is about 118.4917950250.

The spelling of 1663661 in words is "one million, six hundred sixty-three thousand, six hundred sixty-one".