1991969280 has 640 divisors, whose sum is σ = 8485171200. Its totient is φ = 433078272.

The previous prime is 1991969261. The next prime is 1991969293. The reversal of 1991969280 is 829691991.

It is a tau number, because it is divible by the number of its divisors (640).

It is a super-2 number, since 2×1991969280² = 7935883224927436800, which contains 22 as substring.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 11128231 + ... + 11128409.

It is an arithmetic number, because the mean of its divisors is an integer number (13258080).

Almost surely, 2^1991969280 is an apocalyptic number.

1991969280 is a gapful number since it is divisible by the number (10) 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 1991969280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4242585600).

1991969280 is an abundant number, since it is smaller than the sum of its proper divisors (6493201920).

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

1991969280 is a wasteful number, since it uses less digits than its factorization.

1991969280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241 (or 219 counting only the distinct ones).

The product of its (nonzero) digits is 629856, while the sum is 54.

The square root of 1991969280 is about 44631.4830584869. The cubic root of 1991969280 is about 1258.2324422226.

The spelling of 1991969280 in words is "one billion, nine hundred ninety-one million, nine hundred sixty-nine thousand, two hundred eighty".