15511978818 has 64 divisors (see below), whose sum is σ = 39534981120. Its totient is φ = 4416302736.

The previous prime is 15511978793. The next prime is 15511978819. The reversal of 15511978818 is 81887911551.

It is a happy number.

15511978818 is a `hidden beast` number, since 1 + 551 + 1 + 9 + 7 + 8 + 81 + 8 = 666.

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

It is not an unprimeable number, because it can be changed into a prime (15511978819) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34471 + ... + 179477.

It is an arithmetic number, because the mean of its divisors is an integer number (617734080).

Almost surely, 2^15511978818 is an apocalyptic number.

15511978818 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 15511978818, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (19767490560).

15511978818 is an abundant number, since it is smaller than the sum of its proper divisors (24023002302).

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

15511978818 is a wasteful number, since it uses less digits than its factorization.

15511978818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145308 (or 145302 counting only the distinct ones).

The product of its digits is 806400, while the sum is 54.

The spelling of 15511978818 in words is "fifteen billion, five hundred eleven million, nine hundred seventy-eight thousand, eight hundred eighteen".