9991280 has 60 divisors (see below), whose sum is σ = 25188120. Its totient is φ = 3684096.

The previous prime is 9991277. The next prime is 9991297. The reversal of 9991280 is 821999.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13151 + ... + 13889.

It is an arithmetic number, because the mean of its divisors is an integer number (419802).

Almost surely, 2^9991280 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 9991280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (12594060).

9991280 is an abundant number, since it is smaller than the sum of its proper divisors (15196840).

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

9991280 is a wasteful number, since it uses less digits than its factorization.

9991280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 778 (or 759 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 38.

The square root of 9991280 is about 3160.8986064093. The cubic root of 9991280 is about 215.3808285572.

The spelling of 9991280 in words is "nine million, nine hundred ninety-one thousand, two hundred eighty".