1991566080 has 216 divisors, whose sum is σ = 7875303072. Its totient is φ = 455196672.

The previous prime is 1991566061. The next prime is 1991566081. The reversal of 1991566080 is 806651991.

1991566080 is a `hidden beast` number, since 1 + 9 + 9 + 1 + 566 + 0 + 80 = 666.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

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

It is not an unprimeable number, because it can be changed into a prime (1991566081) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 68292 + ... + 92988.

Almost surely, 2^1991566080 is an apocalyptic number.

1991566080 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 1991566080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3937651536).

1991566080 is an abundant number, since it is smaller than the sum of its proper divisors (5883736992).

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

1991566080 is a wasteful number, since it uses less digits than its factorization.

1991566080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24731 (or 24714 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 45.

The square root of 1991566080 is about 44626.9658390530. The cubic root of 1991566080 is about 1258.1475423935.

The spelling of 1991566080 in words is "one billion, nine hundred ninety-one million, five hundred sixty-six thousand, eighty".