21454321565 has 4 divisors (see below), whose sum is σ = 25745185884. Its totient is φ = 17163457248.

The previous prime is 21454321549. The next prime is 21454321583. The reversal of 21454321565 is 56512345412.

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 11383396249 + 10070925316 = 106693^2 + 100354^2 .

It is a cyclic number.

It is not a de Polignac number, because 21454321565 - 2⁴ = 21454321549 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, 2145432152 + ... + 2145432161.

It is an arithmetic number, because the mean of its divisors is an integer number (6436296471).

Almost surely, 2^21454321565 is an apocalyptic number.

It is an amenable number.

21454321565 is a deficient number, since it is larger than the sum of its proper divisors (4290864319).

21454321565 is an equidigital number, since it uses as much as digits as its factorization.

21454321565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4290864318.

The product of its digits is 144000, while the sum is 38.

Adding to 21454321565 its reverse (56512345412), we get a palindrome (77966666977).

The spelling of 21454321565 in words is "twenty-one billion, four hundred fifty-four million, three hundred twenty-one thousand, five hundred sixty-five".