991221792 has 192 divisors, whose sum is σ = 3019161600. Its totient is φ = 281594880.

The previous prime is 991221787. The next prime is 991221793. The reversal of 991221792 is 297122199.

It is not an unprimeable number, because it can be changed into a prime (991221793) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2547934 + ... + 2548322.

It is an arithmetic number, because the mean of its divisors is an integer number (15724800).

Almost surely, 2^991221792 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 991221792, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1509580800).

991221792 is an abundant number, since it is smaller than the sum of its proper divisors (2027939808).

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

991221792 is a wasteful number, since it uses less digits than its factorization.

991221792 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 559 (or 551 counting only the distinct ones).

The product of its digits is 40824, while the sum is 42.

The square root of 991221792 is about 31483.6750078513. The cubic root of 991221792 is about 997.0653267846.

The spelling of 991221792 in words is "nine hundred ninety-one million, two hundred twenty-one thousand, seven hundred ninety-two".