1191721518 has 64 divisors (see below), whose sum is σ = 2874654720. Its totient is φ = 363769056.

The previous prime is 1191721513. The next prime is 1191721547. The reversal of 1191721518 is 8151271911.

1191721518 is a `hidden beast` number, since 119 + 1 + 7 + 21 + 518 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1191721511) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 82471 + ... + 95837.

It is an arithmetic number, because the mean of its divisors is an integer number (44916480).

Almost surely, 2^1191721518 is an apocalyptic number.

1191721518 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1191721518, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1437327360).

1191721518 is an abundant number, since it is smaller than the sum of its proper divisors (1682933202).

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

1191721518 is a wasteful number, since it uses less digits than its factorization.

1191721518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13518 (or 13512 counting only the distinct ones).

The product of its digits is 5040, while the sum is 36.

The square root of 1191721518 is about 34521.3197604031. The cubic root of 1191721518 is about 1060.2092615217.

The spelling of 1191721518 in words is "one billion, one hundred ninety-one million, seven hundred twenty-one thousand, five hundred eighteen".