1991767680 has 288 divisors, whose sum is σ = 8001866340. Its totient is φ = 455196672.

The previous prime is 1991767633. The next prime is 1991767721. The reversal of 1991767680 is 867671991.

It can be written as a sum of positive squares in 2 ways, for example, as 1806590016 + 185177664 = 42504^2 + 13608^2 .

It is a tau number, because it is divible by the number of its divisors (288).

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 278712 + ... + 285768.

Almost surely, 2^1991767680 is an apocalyptic number.

1991767680 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 1991767680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4000933170).

1991767680 is an abundant number, since it is smaller than the sum of its proper divisors (6010098660).

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

1991767680 is a wasteful number, since it uses less digits than its factorization.

1991767680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7096 (or 7074 counting only the distinct ones).

The product of its (nonzero) digits is 1143072, while the sum is 54.

The square root of 1991767680 is about 44629.2245059221. The cubic root of 1991767680 is about 1258.1899937403.

The spelling of 1991767680 in words is "one billion, nine hundred ninety-one million, seven hundred sixty-seven thousand, six hundred eighty".