181221843640 has 32 divisors (see below), whose sum is σ = 417231690480. Its totient is φ = 70802952192.

The previous prime is 181221843631. The next prime is 181221843689. The reversal of 181221843640 is 46348122181.

It is a super-2 number, since 2×181221843640² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 181221843593 and 181221843602.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 52679049 + ... + 52682488.

Almost surely, 2^181221843640 is an apocalyptic number.

181221843640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

181221843640 is an abundant number, since it is smaller than the sum of its proper divisors (236009846840).

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

181221843640 is a wasteful number, since it uses less digits than its factorization.

181221843640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105361591 (or 105361587 counting only the distinct ones).

The product of its (nonzero) digits is 73728, while the sum is 40.

The spelling of 181221843640 in words is "one hundred eighty-one billion, two hundred twenty-one million, eight hundred forty-three thousand, six hundred forty".