1161991980 has 144 divisors (see below), whose sum is σ = 3670771104. Its totient is φ = 308551680.

The previous prime is 1161991979. The next prime is 1161991991. The reversal of 1161991980 is 891991611.

1161991980 is a `hidden beast` number, since 11 + 619 + 9 + 19 + 8 + 0 = 666.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1812460 + ... + 1813100.

It is an arithmetic number, because the mean of its divisors is an integer number (25491466).

Almost surely, 2^1161991980 is an apocalyptic number.

1161991980 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 1161991980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1835385552).

1161991980 is an abundant number, since it is smaller than the sum of its proper divisors (2508779124).

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

1161991980 is a wasteful number, since it uses less digits than its factorization.

1161991980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1038 (or 1024 counting only the distinct ones).

The product of its (nonzero) digits is 34992, while the sum is 45.

The square root of 1161991980 is about 34088.0034616285. The cubic root of 1161991980 is about 1051.3186697517.

The spelling of 1161991980 in words is "one billion, one hundred sixty-one million, nine hundred ninety-one thousand, nine hundred eighty".