1811561066640 has 400 divisors, whose sum is σ = 6819013898928. Its totient is φ = 443079217152.

The previous prime is 1811561066617. The next prime is 1811561066641. The reversal of 1811561066640 is 466601651181.

It can be written as a sum of positive squares in 8 ways, for example, as 64469272464 + 1747091794176 = 253908^2 + 1321776^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (1811561066641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 13157194 + ... + 13294166.

Almost surely, 2^{1811561066640} is an apocalyptic number.

1811561066640 is a gapful number since it is divisible by the number (10) 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 1811561066640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3409506949464).

1811561066640 is an abundant number, since it is smaller than the sum of its proper divisors (5007452832288).

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

1811561066640 is a wasteful number, since it uses less digits than its factorization.

1811561066640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137168 (or 137153 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 45.

The spelling of 1811561066640 in words is "one trillion, eight hundred eleven billion, five hundred sixty-one million, sixty-six thousand, six hundred forty".