991218157977600 has 7680 divisors, whose sum is σ = 4694102678200320. Its totient is φ = 201804742656000.

The previous prime is 991218157977599. The next prime is 991218157977611. The reversal of 991218157977600 is 6779751812199.

991218157977600 is a `hidden beast` number, since 9 + 9 + 1 + 2 + 1 + 8 + 1 + 5 + 7 + 9 + 7 + 7 + 600 = 666.

It is a tau number, because it is divible by the number of its divisors (7680).

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 479 ways as a sum of consecutive naturals, for example, 13578330931164 + ... + 13578330931236.

It is an arithmetic number, because the mean of its divisors is an integer number (611211286224).

Almost surely, 2^{991218157977600} is an apocalyptic number.

991218157977600 is a gapful number since it is divisible by the number (90) 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 991218157977600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2347051339100160).

991218157977600 is an abundant number, since it is smaller than the sum of its proper divisors (3702884520222720).

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

991218157977600 is a wasteful number, since it uses less digits than its factorization.

991218157977600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227 (or 185 counting only the distinct ones).

The product of its (nonzero) digits is 120022560, while the sum is 72.

The spelling of 991218157977600 in words is "nine hundred ninety-one trillion, two hundred eighteen billion, one hundred fifty-seven million, nine hundred seventy-seven thousand, six hundred".