11661155978500 has 768 divisors, whose sum is σ = 32398623129600. Its totient is φ = 3577996800000.

The previous prime is 11661155978299. The next prime is 11661155978503. The reversal of 11661155978500 is 587955116611.

It is a hoax number, since the sum of its digits (55) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (11661155978503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 11421307990 + ... + 11421309010.

It is an arithmetic number, because the mean of its divisors is an integer number (42185707200).

Almost surely, 2^{11661155978500} is an apocalyptic number.

11661155978500 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 11661155978500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16199311564800).

11661155978500 is an abundant number, since it is smaller than the sum of its proper divisors (20737467151100).

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

11661155978500 is a wasteful number, since it uses less digits than its factorization.

11661155978500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1237 (or 1225 counting only the distinct ones).

The product of its (nonzero) digits is 2268000, while the sum is 55.

The spelling of 11661155978500 in words is "eleven trillion, six hundred sixty-one billion, one hundred fifty-five million, nine hundred seventy-eight thousand, five hundred".