1191391980 has 24 divisors (see below), whose sum is σ = 3335897712. Its totient is φ = 317704512.

The previous prime is 1191391967. The next prime is 1191391991. The reversal of 1191391980 is 891931911.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9928207 + ... + 9928326.

It is an arithmetic number, because the mean of its divisors is an integer number (138995738).

Almost surely, 2^1191391980 is an apocalyptic number.

1191391980 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1191391980 is an abundant number, since it is smaller than the sum of its proper divisors (2144505732).

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

1191391980 is a wasteful number, since it uses less digits than its factorization.

1191391980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19856545 (or 19856543 counting only the distinct ones).

The product of its (nonzero) digits is 17496, while the sum is 42.

The square root of 1191391980 is about 34516.5464668759. The cubic root of 1191391980 is about 1060.1115285522. Note that the first 3 decimals are identical.

The spelling of 1191391980 in words is "one billion, one hundred ninety-one million, three hundred ninety-one thousand, nine hundred eighty".