21618987712 has 28 divisors (see below), whose sum is σ = 49028776720. Its totient is φ = 9265280256.

The previous prime is 21618987707. The next prime is 21618987727. The reversal of 21618987712 is 21778981612.

It is a tau number, because it is divible by the number of its divisors (28).

It is a self number, because there is not a number n which added to its sum of digits gives 21618987712.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24127887 + ... + 24128782.

It is an arithmetic number, because the mean of its divisors is an integer number (1751027740).

Almost surely, 2^21618987712 is an apocalyptic number.

It is an amenable number.

21618987712 is an abundant number, since it is smaller than the sum of its proper divisors (27409789008).

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

21618987712 is an equidigital number, since it uses as much as digits as its factorization.

21618987712 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48256688 (or 48256678 counting only the distinct ones).

The product of its digits is 677376, while the sum is 52.

The spelling of 21618987712 in words is "twenty-one billion, six hundred eighteen million, nine hundred eighty-seven thousand, seven hundred twelve".