21055503551365 has 4 divisors (see below), whose sum is σ = 25266604261644. Its totient is φ = 16844402841088.

The previous prime is 21055503551347. The next prime is 21055503551393. The reversal of 21055503551365 is 56315530555012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16610629476996 + 4444874074369 = 4075614^2 + 2108287^2 .

It is a cyclic number.

It is not a de Polignac number, because 21055503551365 - 2⁷ = 21055503551237 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2105550355132 + ... + 2105550355141.

It is an arithmetic number, because the mean of its divisors is an integer number (6316651065411).

Almost surely, 2^{21055503551365} is an apocalyptic number.

It is an amenable number.

21055503551365 is a deficient number, since it is larger than the sum of its proper divisors (4211100710279).

21055503551365 is an equidigital number, since it uses as much as digits as its factorization.

21055503551365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4211100710278.

The product of its (nonzero) digits is 1687500, while the sum is 46.

The spelling of 21055503551365 in words is "twenty-one trillion, fifty-five billion, five hundred three million, five hundred fifty-one thousand, three hundred sixty-five".