21455553203555 has 16 divisors (see below), whose sum is σ = 28446441897024. Its totient is φ = 15452388188160.

The previous prime is 21455553203549. The next prime is 21455553203621. The reversal of 21455553203555 is 55530235555412.

It is not a de Polignac number, because 21455553203555 - 2²⁰ = 21455552154979 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5487351806 + ... + 5487355715.

It is an arithmetic number, because the mean of its divisors is an integer number (1777902618564).

Almost surely, 2^{21455553203555} is an apocalyptic number.

21455553203555 is a deficient number, since it is larger than the sum of its proper divisors (6990888693469).

21455553203555 is a wasteful number, since it uses less digits than its factorization.

21455553203555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10974707566.

The product of its (nonzero) digits is 11250000, while the sum is 50.

Adding to 21455553203555 its reverse (55530235555412), we get a palindrome (76985788758967).

The spelling of 21455553203555 in words is "twenty-one trillion, four hundred fifty-five billion, five hundred fifty-three million, two hundred three thousand, five hundred fifty-five".