991393280 has 40 divisors (see below), whose sum is σ = 2377026432. Its totient is φ = 396556288.

The previous prime is 991393223. The next prime is 991393283. The reversal of 991393280 is 82393199.

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991393283) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 191072 + ... + 196191.

Almost surely, 2^991393280 is an apocalyptic number.

It is an amenable number.

991393280 is an abundant number, since it is smaller than the sum of its proper divisors (1385633152).

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

991393280 is an equidigital number, since it uses as much as digits as its factorization.

991393280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 387286 (or 387270 counting only the distinct ones).

The product of its (nonzero) digits is 104976, while the sum is 44.

The square root of 991393280 is about 31486.3983332486. The cubic root of 991393280 is about 997.1228231258.

The spelling of 991393280 in words is "nine hundred ninety-one million, three hundred ninety-three thousand, two hundred eighty".