1991185560 has 576 divisors, whose sum is σ = 8552325600. Its totient is φ = 397135872.

The previous prime is 1991185531. The next prime is 1991185561. The reversal of 1991185560 is 655811991.

1991185560 is a `hidden beast` number, since 1 + 9 + 9 + 1 + 1 + 85 + 560 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991185561) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 4356852 + ... + 4357308.

Almost surely, 2^1991185560 is an apocalyptic number.

1991185560 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 1991185560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4276162800).

1991185560 is an abundant number, since it is smaller than the sum of its proper divisors (6561140040).

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

1991185560 is a wasteful number, since it uses less digits than its factorization.

1991185560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520 (or 506 counting only the distinct ones).

The product of its (nonzero) digits is 97200, while the sum is 45.

The square root of 1991185560 is about 44622.7022937876. The cubic root of 1991185560 is about 1258.0674076691.

The spelling of 1991185560 in words is "one billion, nine hundred ninety-one million, one hundred eighty-five thousand, five hundred sixty".