1991406384 has 420 divisors, whose sum is σ = 6813735768. Its totient is φ = 561116160.

The previous prime is 1991406349. The next prime is 1991406407. The reversal of 1991406384 is 4836041991.

1991406384 is a `hidden beast` number, since 1 + 9 + 9 + 1 + 4 + 0 + 638 + 4 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 83 ways as a sum of consecutive naturals, for example, 23992807 + ... + 23992889.

Almost surely, 2^1991406384 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 1991406384, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3406867884).

1991406384 is an abundant number, since it is smaller than the sum of its proper divisors (4822329384).

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

1991406384 is a wasteful number, since it uses less digits than its factorization.

1991406384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148 (or 116 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 45.

The square root of 1991406384 is about 44625.1765710792. The cubic root of 1991406384 is about 1258.1139128289.

The spelling of 1991406384 in words is "one billion, nine hundred ninety-one million, four hundred six thousand, three hundred eighty-four".