991333980 has 144 divisors (see below), whose sum is σ = 3701041344. Its totient is φ = 209157120.

The previous prime is 991333927. The next prime is 991334033. The reversal of 991333980 is 89333199.

It is an interprime number because it is at equal distance from previous prime (991333927) and next prime (991334033).

It is a Harshad number since it is a multiple of its sum of digits (45).

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, 13881 + ... + 46640.

It is an arithmetic number, because the mean of its divisors is an integer number (25701676).

Almost surely, 2^991333980 is an apocalyptic number.

991333980 is a gapful number since it is divisible by the number (90) 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 991333980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1850520672).

991333980 is an abundant number, since it is smaller than the sum of its proper divisors (2709707364).

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

991333980 is a wasteful number, since it uses less digits than its factorization.

991333980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60556 (or 60551 counting only the distinct ones).

The product of its (nonzero) digits is 157464, while the sum is 45.

The square root of 991333980 is about 31485.4566427105. The cubic root of 991333980 is about 997.1029418256.

It can be divided in two parts, 991 and 333980, that added together give a triangular number (334971 = T₈₁₈).

The spelling of 991333980 in words is "nine hundred ninety-one million, three hundred thirty-three thousand, nine hundred eighty".