21481195565 has 4 divisors (see below), whose sum is σ = 25777434684. Its totient is φ = 17184956448.

The previous prime is 21481195537. The next prime is 21481195577. The reversal of 21481195565 is 56559118412.

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 6734007721 + 14747187844 = 82061^2 + 121438^2 .

It is a cyclic number.

It is not a de Polignac number, because 21481195565 - 2¹⁰ = 21481194541 is a prime.

It is a super-2 number, since 2×21481195565² (a number of 21 digits) contains 22 as substring.

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, 2148119552 + ... + 2148119561.

It is an arithmetic number, because the mean of its divisors is an integer number (6444358671).

Almost surely, 2^21481195565 is an apocalyptic number.

It is an amenable number.

21481195565 is a deficient number, since it is larger than the sum of its proper divisors (4296239119).

21481195565 is an equidigital number, since it uses as much as digits as its factorization.

21481195565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4296239118.

The product of its digits is 432000, while the sum is 47.

The spelling of 21481195565 in words is "twenty-one billion, four hundred eighty-one million, one hundred ninety-five thousand, five hundred sixty-five".