21005500020 has 48 divisors (see below), whose sum is σ = 58826156928. Its totient is φ = 5600442240.

The previous prime is 21005499997. The next prime is 21005500031. The reversal of 21005500020 is 2000550012.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 333225 + ... + 391215.

It is an arithmetic number, because the mean of its divisors is an integer number (1225544936).

Almost surely, 2^21005500020 is an apocalyptic number.

21005500020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21005500020 is an abundant number, since it is smaller than the sum of its proper divisors (37820656908).

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

21005500020 is a wasteful number, since it uses less digits than its factorization.

21005500020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64040 (or 64038 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 15.

The spelling of 21005500020 in words is "twenty-one billion, five million, five hundred thousand, twenty".