21455816285 has 4 divisors (see below), whose sum is σ = 25746979548. Its totient is φ = 17164653024.

The previous prime is 21455816227. The next prime is 21455816287. The reversal of 21455816285 is 58261855412.

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 12569548996 + 8886267289 = 112114^2 + 94267^2 .

It is a cyclic number.

It is not a de Polignac number, because 21455816285 - 2¹⁰ = 21455815261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21455816287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2145581624 + ... + 2145581633.

It is an arithmetic number, because the mean of its divisors is an integer number (6436744887).

Almost surely, 2^21455816285 is an apocalyptic number.

It is an amenable number.

21455816285 is a deficient number, since it is larger than the sum of its proper divisors (4291163263).

21455816285 is an equidigital number, since it uses as much as digits as its factorization.

21455816285 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4291163262.

The product of its digits is 768000, while the sum is 47.

The spelling of 21455816285 in words is "twenty-one billion, four hundred fifty-five million, eight hundred sixteen thousand, two hundred eighty-five".