1991615915520 has 960 divisors, whose sum is σ = 8896277744640. Its totient is φ = 399561523200.

The previous prime is 1991615915507. The next prime is 1991615915539. The reversal of 1991615915520 is 255195161991.

It is a happy number.

1991615915520 is a `hidden beast` number, since 1 + 9 + 9 + 1 + 61 + 59 + 1 + 5 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (960).

It is a super-3 number, since 3×1991615915520³ (a number of 38 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 51428965 + ... + 51467675.

It is an arithmetic number, because the mean of its divisors is an integer number (9266955984).

Almost surely, 2^{1991615915520} is an apocalyptic number.

1991615915520 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 1991615915520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4448138872320).

1991615915520 is an abundant number, since it is smaller than the sum of its proper divisors (6904661829120).

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

1991615915520 is a wasteful number, since it uses less digits than its factorization.

1991615915520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38787 (or 38768 counting only the distinct ones).

The product of its (nonzero) digits is 1093500, while the sum is 54.

The spelling of 1991615915520 in words is "one trillion, nine hundred ninety-one billion, six hundred fifteen million, nine hundred fifteen thousand, five hundred twenty".