1161781566 has 64 divisors (see below), whose sum is σ = 2659516416. Its totient is φ = 334901600.

The previous prime is 1161781561. The next prime is 1161781573. The reversal of 1161781566 is 6651871611.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1161781561) 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 31 ways as a sum of consecutive naturals, for example, 287935 + ... + 291941.

It is an arithmetic number, because the mean of its divisors is an integer number (41554944).

Almost surely, 2^1161781566 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1161781566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1329758208).

1161781566 is an abundant number, since it is smaller than the sum of its proper divisors (1497734850).

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

1161781566 is a wasteful number, since it uses less digits than its factorization.

1161781566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4237.

The product of its digits is 60480, while the sum is 42.

The square root of 1161781566 is about 34084.9169868433. The cubic root of 1161781566 is about 1051.2552081776.

The spelling of 1161781566 in words is "one billion, one hundred sixty-one million, seven hundred eighty-one thousand, five hundred sixty-six".