991974816 has 144 divisors (see below), whose sum is σ = 3365772480. Its totient is φ = 283409280.

The previous prime is 991974811. The next prime is 991974817. The reversal of 991974816 is 618479199.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (991974811) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 30621 + ... + 54051.

It is an arithmetic number, because the mean of its divisors is an integer number (23373420).

Almost surely, 2^991974816 is an apocalyptic number.

991974816 is a gapful number since it is divisible by the number (96) 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 991974816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1682886240).

991974816 is an abundant number, since it is smaller than the sum of its proper divisors (2373797664).

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

991974816 is a wasteful number, since it uses less digits than its factorization.

991974816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23464 (or 23443 counting only the distinct ones).

The product of its digits is 979776, while the sum is 54.

The square root of 991974816 is about 31495.6316971100. The cubic root of 991974816 is about 997.3177506375.

The spelling of 991974816 in words is "nine hundred ninety-one million, nine hundred seventy-four thousand, eight hundred sixteen".