1781536661856 has 336 divisors, whose sum is σ = 6203823510528. Its totient is φ = 492589382400.

The previous prime is 1781536661851. The next prime is 1781536661881. The reversal of 1781536661856 is 6581666351871.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (336).

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a junction number, because it is equal to n+sod(n) for n = 1781536661793 and 1781536661802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1781536661851) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 4886211 + ... + 5238141.

It is an arithmetic number, because the mean of its divisors is an integer number (18463760448).

Almost surely, 2^{1781536661856} is an apocalyptic number.

1781536661856 is a gapful number since it is divisible by the number (16) 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 1781536661856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3101911755264).

1781536661856 is an abundant number, since it is smaller than the sum of its proper divisors (4422286848672).

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

1781536661856 is an equidigital number, since it uses as much as digits as its factorization.

1781536661856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 351997 (or 351974 counting only the distinct ones).

The product of its digits is 43545600, while the sum is 63.

The spelling of 1781536661856 in words is "one trillion, seven hundred eighty-one billion, five hundred thirty-six million, six hundred sixty-one thousand, eight hundred fifty-six".