661005 has 24 divisors (see below), whose sum is σ = 1179672. Its totient is φ = 342144.

The previous prime is 660983. The next prime is 661009. The reversal of 661005 is 500166.

661005 is a `hidden beast` number, since 661 + 0 + 0 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 233289 + 427716 = 483^2 + 654^2 .

It is not a de Polignac number, because 661005 - 2⁵ = 660973 is a prime.

It is a super-2 number, since 2×661005² = 873855220050, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

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

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1467 + ... + 1863.

It is an arithmetic number, because the mean of its divisors is an integer number (49153).

2⁶⁶¹⁰⁰⁵ is an apocalyptic number.

It is an amenable number.

661005 is a deficient number, since it is larger than the sum of its proper divisors (518667).

661005 is a wasteful number, since it uses less digits than its factorization.

661005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 445 (or 442 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 661005 is about 813.0221399199. The cubic root of 661005 is about 87.1100470281.

The spelling of 661005 in words is "six hundred sixty-one thousand, five".