1991451672 has 192 divisors, whose sum is σ = 6686971200. Its totient is φ = 522362880.

The previous prime is 1991451659. The next prime is 1991451673. The reversal of 1991451672 is 2761541991.

1991451672 is a `hidden beast` number, since 199 + 1 + 451 + 6 + 7 + 2 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991451673) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 348454 + ... + 354122.

It is an arithmetic number, because the mean of its divisors is an integer number (34827975).

Almost surely, 2^1991451672 is an apocalyptic number.

1991451672 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 1991451672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3343485600).

1991451672 is an abundant number, since it is smaller than the sum of its proper divisors (4695519528).

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

1991451672 is a wasteful number, since it uses less digits than its factorization.

1991451672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5746 (or 5739 counting only the distinct ones).

The product of its digits is 136080, while the sum is 45.

The square root of 1991451672 is about 44625.6839947580. The cubic root of 1991451672 is about 1258.1234499801.

The spelling of 1991451672 in words is "one billion, nine hundred ninety-one million, four hundred fifty-one thousand, six hundred seventy-two".