1991711568 has 160 divisors (see below), whose sum is σ = 6792422400. Its totient is φ = 486881280.

The previous prime is 1991711543. The next prime is 1991711587. The reversal of 1991711568 is 8651171991.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

It is an unprimeable number.

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, 46983 + ... + 78681.

It is an arithmetic number, because the mean of its divisors is an integer number (42452640).

Almost surely, 2^1991711568 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1991711568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3396211200).

1991711568 is an abundant number, since it is smaller than the sum of its proper divisors (4800710832).

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

1991711568 is a wasteful number, since it uses less digits than its factorization.

1991711568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31745 (or 31739 counting only the distinct ones).

The product of its digits is 136080, while the sum is 48.

The square root of 1991711568 is about 44628.5958551241. The cubic root of 1991711568 is about 1258.1781784031.

The spelling of 1991711568 in words is "one billion, nine hundred ninety-one million, seven hundred eleven thousand, five hundred sixty-eight".