991361280 has 288 divisors, whose sum is σ = 3898185984. Its totient is φ = 209092608.

The previous prime is 991361269. The next prime is 991361297. The reversal of 991361280 is 82163199.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 348022 + ... + 350858.

It is an arithmetic number, because the mean of its divisors is an integer number (13535368).

Almost surely, 2^991361280 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 991361280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1949092992).

991361280 is an abundant number, since it is smaller than the sum of its proper divisors (2906824704).

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

991361280 is a wasteful number, since it uses less digits than its factorization.

991361280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2881 (or 2867 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 39.

The square root of 991361280 is about 31485.8901732189. The cubic root of 991361280 is about 997.1120946980.

The spelling of 991361280 in words is "nine hundred ninety-one million, three hundred sixty-one thousand, two hundred eighty".