1991372544 has 324 divisors, whose sum is σ = 6906594240. Its totient is φ = 549642240.

The previous prime is 1991372533. The next prime is 1991372549. The reversal of 1991372544 is 4452731991.

1991372544 is a `hidden beast` number, since 1 + 99 + 13 + 7 + 2 + 544 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 1991372544.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991372549) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 3499492 + ... + 3500060.

Almost surely, 2^1991372544 is an apocalyptic number.

1991372544 is a gapful number since it is divisible by the number (14) 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 1991372544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3453297120).

1991372544 is an abundant number, since it is smaller than the sum of its proper divisors (4915221696).

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

1991372544 is a wasteful number, since it uses less digits than its factorization.

1991372544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 636 (or 612 counting only the distinct ones).

The product of its digits is 272160, while the sum is 45.

The square root of 1991372544 is about 44624.7974113048. The cubic root of 1991372544 is about 1258.1067864054.

The spelling of 1991372544 in words is "one billion, nine hundred ninety-one million, three hundred seventy-two thousand, five hundred forty-four".