661081 has 4 divisors (see below), whose sum is σ = 670464. Its totient is φ = 651700.

The previous prime is 661061. The next prime is 661091. The reversal of 661081 is 180166.

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 661081 - 2⁵ = 661049 is a prime.

It is a super-2 number, since 2×661081² = 874056177122, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661061) 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, 4585 + ... + 4726.

It is an arithmetic number, because the mean of its divisors is an integer number (167616).

2⁶⁶¹⁰⁸¹ is an apocalyptic number.

It is an amenable number.

661081 is a deficient number, since it is larger than the sum of its proper divisors (9383).

661081 is an equidigital number, since it uses as much as digits as its factorization.

661081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9382.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 661081 is about 813.0688777711. The cubic root of 661081 is about 87.1133854344.

The spelling of 661081 in words is "six hundred sixty-one thousand, eighty-one".