1661500661605 has 8 divisors (see below), whose sum is σ = 1995999036192. Its totient is φ = 1327735034448.

The previous prime is 1661500661549. The next prime is 1661500661609. The reversal of 1661500661605 is 5061660051661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1661500661605 - 2¹¹ = 1661500659557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661500661609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 183181867 + ... + 183190936.

It is an arithmetic number, because the mean of its divisors is an integer number (249499879524).

Almost surely, 2^{1661500661605} is an apocalyptic number.

It is an amenable number.

1661500661605 is a deficient number, since it is larger than the sum of its proper divisors (334498374587).

1661500661605 is an equidigital number, since it uses as much as digits as its factorization.

1661500661605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 366373715.

The product of its (nonzero) digits is 194400, while the sum is 43.

The spelling of 1661500661605 in words is "one trillion, six hundred sixty-one billion, five hundred million, six hundred sixty-one thousand, six hundred five".