1661874782791 has 16 divisors (see below), whose sum is σ = 1725069443328. Its totient is φ = 1599287558400.

The previous prime is 1661874782761. The next prime is 1661874782803. The reversal of 1661874782791 is 1972874781661.

It is a cyclic number.

It is not a de Polignac number, because 1661874782791 - 2¹⁵ = 1661874750023 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 (1661874782731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12102981 + ... + 12239521.

It is an arithmetic number, because the mean of its divisors is an integer number (107816840208).

Almost surely, 2^{1661874782791} is an apocalyptic number.

1661874782791 is a deficient number, since it is larger than the sum of its proper divisors (63194660537).

1661874782791 is a wasteful number, since it uses less digits than its factorization.

1661874782791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138762.

The product of its digits is 56899584, while the sum is 67.

The spelling of 1661874782791 in words is "one trillion, six hundred sixty-one billion, eight hundred seventy-four million, seven hundred eighty-two thousand, seven hundred ninety-one".