21144321505 has 4 divisors (see below), whose sum is σ = 25373185812. Its totient is φ = 16915457200.

The previous prime is 21144321461. The next prime is 21144321547. The reversal of 21144321505 is 50512344112.

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 11943866944 + 9200454561 = 109288^2 + 95919^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21144321505 is a prime.

It is a Duffinian number.

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 3 ways as a sum of consecutive naturals, for example, 2114432146 + ... + 2114432155.

It is an arithmetic number, because the mean of its divisors is an integer number (6343296453).

Almost surely, 2^21144321505 is an apocalyptic number.

It is an amenable number.

21144321505 is a deficient number, since it is larger than the sum of its proper divisors (4228864307).

21144321505 is an equidigital number, since it uses as much as digits as its factorization.

21144321505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4228864306.

The product of its (nonzero) digits is 4800, while the sum is 28.

Adding to 21144321505 its reverse (50512344112), we get a palindrome (71656665617).

The spelling of 21144321505 in words is "twenty-one billion, one hundred forty-four million, three hundred twenty-one thousand, five hundred five".