1661880768768 has 270 divisors, whose sum is σ = 5446883353142. Its totient is φ = 503599472640.

The previous prime is 1661880768721. The next prime is 1661880768781. The reversal of 1661880768768 is 8678670881661.

It can be written as a sum of positive squares in only one way, i.e., 1102903236864 + 558977531904 = 1050192^2 + 747648^2 .

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a junction number, because it is equal to n+sod(n) for n = 1661880768696 and 1661880768705.

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 2177880 + ... + 2840232.

Almost surely, 2^{1661880768768} is an apocalyptic number.

1661880768768 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1661880768768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2723441676571).

1661880768768 is an abundant number, since it is smaller than the sum of its proper divisors (3785002584374).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1661880768768 is an equidigital number, since it uses as much as digits as its factorization.

1661880768768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 662403 (or 662369 counting only the distinct ones).

The product of its (nonzero) digits is 260112384, while the sum is 72.

The spelling of 1661880768768 in words is "one trillion, six hundred sixty-one billion, eight hundred eighty million, seven hundred sixty-eight thousand, seven hundred sixty-eight".