17978165856 has 432 divisors, whose sum is σ = 63546393456. Its totient is φ = 4790403072.

The previous prime is 17978165833. The next prime is 17978165867. The reversal of 17978165856 is 65856187971.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a junction number, because it is equal to n+sod(n) for n = 17978165793 and 17978165802.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 32866575 + ... + 32867121.

It is an arithmetic number, because the mean of its divisors is an integer number (147098133).

Almost surely, 2^17978165856 is an apocalyptic number.

17978165856 is a gapful number since it is divisible by the number (16) 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 17978165856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31773196728).

17978165856 is an abundant number, since it is smaller than the sum of its proper divisors (45568227600).

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

17978165856 is a wasteful number, since it uses less digits than its factorization.

17978165856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 731 (or 713 counting only the distinct ones).

The product of its digits is 25401600, while the sum is 63.

The spelling of 17978165856 in words is "seventeen billion, nine hundred seventy-eight million, one hundred sixty-five thousand, eight hundred fifty-six".