1991518682400 has 2160 divisors, whose sum is σ = 8452452836520. Its totient is φ = 453272371200.

The previous prime is 1991518682399. The next prime is 1991518682411. The reversal of 1991518682400 is 42868151991.

1991518682400 is a `hidden beast` number, since 1 + 9 + 9 + 1 + 518 + 6 + 82 + 40 + 0 = 666.

It can be written as a sum of positive squares in 12 ways, for example, as 31104260496 + 1960414421904 = 176364^2 + 1400148^2 .

It is a tau number, because it is divible by the number of its divisors (2160).

It is a super-2 number, since 2×1991518682400² (a number of 25 digits) contains 22 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 359 ways as a sum of consecutive naturals, for example, 18270813546 + ... + 18270813654.

Almost surely, 2^{1991518682400} is an apocalyptic number.

1991518682400 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 1991518682400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4226226418260).

1991518682400 is an abundant number, since it is smaller than the sum of its proper divisors (6460934154120).

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

1991518682400 is a wasteful number, since it uses less digits than its factorization.

1991518682400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 54.

The spelling of 1991518682400 in words is "one trillion, nine hundred ninety-one billion, five hundred eighteen million, six hundred eighty-two thousand, four hundred".