991323040 has 96 divisors (see below), whose sum is σ = 2490508944. Its totient is φ = 371589120.

The previous prime is 991323031. The next prime is 991323049. The reversal of 991323040 is 40323199.

It is an interprime number because it is at equal distance from previous prime (991323031) and next prime (991323049).

It can be written as a sum of positive squares in 8 ways, for example, as 928786576 + 62536464 = 30476^2 + 7908^2 .

It is a junction number, because it is equal to n+sod(n) for n = 991322993 and 991323011.

It is not an unprimeable number, because it can be changed into a prime (991323049) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 763672 + ... + 764968.

Almost surely, 2^991323040 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 991323040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1245254472).

991323040 is an abundant number, since it is smaller than the sum of its proper divisors (1499185904).

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

991323040 is a wasteful number, since it uses less digits than its factorization.

991323040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1610 (or 1602 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 31.

The square root of 991323040 is about 31485.2829112270. The cubic root of 991323040 is about 997.0992739240.

The spelling of 991323040 in words is "nine hundred ninety-one million, three hundred twenty-three thousand, forty".