21855866784 has 48 divisors (see below), whose sum is σ = 57552713568. Its totient is φ = 7262296832.

The previous prime is 21855866749. The next prime is 21855866803. The reversal of 21855866784 is 48766855812.

It is a tau number, because it is divible by the number of its divisors (48).

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, 328662 + ... + 389525.

It is an arithmetic number, because the mean of its divisors is an integer number (1199014866).

Almost surely, 2^21855866784 is an apocalyptic number.

21855866784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21855866784 is an abundant number, since it is smaller than the sum of its proper divisors (35696846784).

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

21855866784 is a wasteful number, since it uses less digits than its factorization.

21855866784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 718517 (or 718509 counting only the distinct ones).

The product of its digits is 25804800, while the sum is 60.

The spelling of 21855866784 in words is "twenty-one billion, eight hundred fifty-five million, eight hundred sixty-six thousand, seven hundred eighty-four".