21405500555 has 12 divisors (see below), whose sum is σ = 26043324480. Its totient is φ = 16889798592.

The previous prime is 21405500509. The next prime is 21405500563. The reversal of 21405500555 is 55500550412.

It is not a de Polignac number, because 21405500555 - 2¹² = 21405496459 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 375035 + ... + 428324.

It is an arithmetic number, because the mean of its divisors is an integer number (2170277040).

Almost surely, 2^21405500555 is an apocalyptic number.

21405500555 is a deficient number, since it is larger than the sum of its proper divisors (4637823925).

21405500555 is an frugal number, since it uses more digits than its factorization.

21405500555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 803510 (or 803437 counting only the distinct ones).

The product of its (nonzero) digits is 25000, while the sum is 32.

The spelling of 21405500555 in words is "twenty-one billion, four hundred five million, five hundred thousand, five hundred fifty-five".