1991209472 has 120 divisors (see below), whose sum is σ = 4669544880. Its totient is φ = 845752320.

The previous prime is 1991209463. The next prime is 1991209511. The reversal of 1991209472 is 2749021991.

It is a super-2 number, since 2×1991209472² = 7929830322765037568, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3486947 + ... + 3487517.

It is an arithmetic number, because the mean of its divisors is an integer number (38912874).

Almost surely, 2^1991209472 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 1991209472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2334772440).

1991209472 is an abundant number, since it is smaller than the sum of its proper divisors (2678335408).

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

1991209472 is an equidigital number, since it uses as much as digits as its factorization.

1991209472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 742 (or 719 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 44.

The square root of 1991209472 is about 44622.9702283476. The cubic root of 1991209472 is about 1258.0724436618.

The spelling of 1991209472 in words is "one billion, nine hundred ninety-one million, two hundred nine thousand, four hundred seventy-two".