181286521920 has 672 divisors, whose sum is σ = 742765510656. Its totient is φ = 39710822400.

The previous prime is 181286521873. The next prime is 181286521921. The reversal of 181286521920 is 29125682181.

181286521920 is a `hidden beast` number, since 1 + 81 + 28 + 6 + 521 + 9 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (672).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (181286521921) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 66869365 + ... + 66872075.

Almost surely, 2^181286521920 is an apocalyptic number.

181286521920 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 181286521920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (371382755328).

181286521920 is an abundant number, since it is smaller than the sum of its proper divisors (561478988736).

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

181286521920 is a wasteful number, since it uses less digits than its factorization.

181286521920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2879 (or 2866 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 45.

The spelling of 181286521920 in words is "one hundred eighty-one billion, two hundred eighty-six million, five hundred twenty-one thousand, nine hundred twenty".