1991624840 has 64 divisors (see below), whose sum is σ = 4773988800. Its totient is φ = 745604352.

The previous prime is 1991624801. The next prime is 1991624857. The reversal of 1991624840 is 484261991.

It is a junction number, because it is equal to n+sod(n) for n = 1991624791 and 1991624800.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47294 + ... + 78866.

It is an arithmetic number, because the mean of its divisors is an integer number (74593575).

Almost surely, 2^1991624840 is an apocalyptic number.

1991624840 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 1991624840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2386994400).

1991624840 is an abundant number, since it is smaller than the sum of its proper divisors (2782363960).

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

1991624840 is a wasteful number, since it uses less digits than its factorization.

1991624840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31686 (or 31682 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 44.

The square root of 1991624840 is about 44627.6241805454. The cubic root of 1991624840 is about 1258.1599159093.

The spelling of 1991624840 in words is "one billion, nine hundred ninety-one million, six hundred twenty-four thousand, eight hundred forty".