991243512 has 192 divisors, whose sum is σ = 3224033280. Its totient is φ = 269001216.

The previous prime is 991243457. The next prime is 991243537. The reversal of 991243512 is 215342199.

991243512 is a `hidden beast` number, since 99 + 12 + 43 + 512 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2700753 + ... + 2701119.

It is an arithmetic number, because the mean of its divisors is an integer number (16791840).

Almost surely, 2^991243512 is an apocalyptic number.

991243512 is a gapful number since it is divisible by the number (92) 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 991243512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1612016640).

991243512 is an abundant number, since it is smaller than the sum of its proper divisors (2232789768).

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

991243512 is a wasteful number, since it uses less digits than its factorization.

991243512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 642 (or 635 counting only the distinct ones).

The product of its digits is 19440, while the sum is 36.

The square root of 991243512 is about 31484.0199466332. The cubic root of 991243512 is about 997.0726094132.

The spelling of 991243512 in words is "nine hundred ninety-one million, two hundred forty-three thousand, five hundred twelve".