1661501782161 has 40 divisors (see below), whose sum is σ = 2813599293120. Its totient is φ = 968648800608.

The previous prime is 1661501782159. The next prime is 1661501782169. The reversal of 1661501782161 is 1612871051661.

1661501782161 is a `hidden beast` number, since 1 + 6 + 6 + 1 + 501 + 7 + 82 + 1 + 61 = 666.

It is not a de Polignac number, because 1661501782161 - 2¹ = 1661501782159 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1661501782169) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 41503005 + ... + 41543018.

It is an arithmetic number, because the mean of its divisors is an integer number (70339982328).

Almost surely, 2^{1661501782161} is an apocalyptic number.

It is an amenable number.

1661501782161 is a deficient number, since it is larger than the sum of its proper divisors (1152097510959).

1661501782161 is a wasteful number, since it uses less digits than its factorization.

1661501782161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83046067 (or 83046058 counting only the distinct ones).

The product of its (nonzero) digits is 120960, while the sum is 45.

The spelling of 1661501782161 in words is "one trillion, six hundred sixty-one billion, five hundred one million, seven hundred eighty-two thousand, one hundred sixty-one".