1991388672 has 320 divisors, whose sum is σ = 7259535360. Its totient is φ = 524869632.

The previous prime is 1991388667. The next prime is 1991388677. The reversal of 1991388672 is 2768831991.

1991388672 is a `hidden beast` number, since 199 + 1 + 388 + 6 + 72 = 666.

It is an interprime number because it is at equal distance from previous prime (1991388667) and next prime (1991388677).

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991388677) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 1257193 + ... + 1258775.

It is an arithmetic number, because the mean of its divisors is an integer number (22686048).

Almost surely, 2^1991388672 is an apocalyptic number.

1991388672 is a gapful number since it is divisible by the number (12) 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 1991388672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3629767680).

1991388672 is an abundant number, since it is smaller than the sum of its proper divisors (5268146688).

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

1991388672 is a wasteful number, since it uses less digits than its factorization.

1991388672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1630 (or 1608 counting only the distinct ones).

The product of its digits is 1306368, while the sum is 54.

The square root of 1991388672 is about 44624.9781176417. The cubic root of 1991388672 is about 1258.1101828386.

The spelling of 1991388672 in words is "one billion, nine hundred ninety-one million, three hundred eighty-eight thousand, six hundred seventy-two".