581661 has 20 divisors (see below), whose sum is σ = 894432. Its totient is φ = 376488.

The previous prime is 581657. The next prime is 581663. The reversal of 581661 is 166185.

It is not a de Polignac number, because 581661 - 2² = 581657 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 581661.

It is not an unprimeable number, because it can be changed into a prime (581663) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3400 + ... + 3566.

2⁵⁸¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

581661 is a deficient number, since it is larger than the sum of its proper divisors (312771).

581661 is a wasteful number, since it uses less digits than its factorization.

581661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 222 (or 213 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 581661 is about 762.6670308857. The cubic root of 581661 is about 83.4750424413.

The spelling of 581661 in words is "five hundred eighty-one thousand, six hundred sixty-one".