661001 has 4 divisors (see below), whose sum is σ = 721104. Its totient is φ = 600900.

The previous prime is 660983. The next prime is 661009. The reversal of 661001 is 100166.

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 661001 - 2¹⁴ = 644617 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (661009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30035 + ... + 30056.

It is an arithmetic number, because the mean of its divisors is an integer number (180276).

2⁶⁶¹⁰⁰¹ is an apocalyptic number.

It is an amenable number.

661001 is a deficient number, since it is larger than the sum of its proper divisors (60103).

661001 is a wasteful number, since it uses less digits than its factorization.

661001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60102.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 661001 is about 813.0196799586. The cubic root of 661001 is about 87.1098713154.

Adding to 661001 its reverse (100166), we get a palindrome (761167).

It can be divided in two parts, 66 and 1001, that multiplied together give a palindrome (66066).

The spelling of 661001 in words is "six hundred sixty-one thousand, one".