1661001 has 4 divisors (see below), whose sum is σ = 2214672. Its totient is φ = 1107332.

The previous prime is 1660963. The next prime is 1661003. The reversal of 1661001 is 1001661.

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 1661001 - 2⁷ = 1660873 is a prime.

It is a D-number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1661003) 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, 276831 + ... + 276836.

It is an arithmetic number, because the mean of its divisors is an integer number (553668).

2^1661001 is an apocalyptic number.

It is an amenable number.

1661001 is a deficient number, since it is larger than the sum of its proper divisors (553671).

1661001 is an equidigital number, since it uses as much as digits as its factorization.

1661001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553670.

The product of its (nonzero) digits is 36, while the sum is 15.

The square root of 1661001 is about 1288.7982774663. The cubic root of 1661001 is about 118.4286098153.

Adding to 1661001 its reverse (1001661), we get a palindrome (2662662).

The spelling of 1661001 in words is "one million, six hundred sixty-one thousand, one".