21255216322565 has 8 divisors (see below), whose sum is σ = 25506869117568. Its totient is φ = 17003766704400.

The previous prime is 21255216322559. The next prime is 21255216322573. The reversal of 21255216322565 is 56522361255212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-21255216322565 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 7 ways as a sum of consecutive naturals, for example, 50563961 + ... + 50982590.

It is an arithmetic number, because the mean of its divisors is an integer number (3188358639696).

Almost surely, 2^{21255216322565} is an apocalyptic number.

It is an amenable number.

21255216322565 is a deficient number, since it is larger than the sum of its proper divisors (4251652795003).

21255216322565 is a wasteful number, since it uses less digits than its factorization.

21255216322565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101588419.

The product of its digits is 2160000, while the sum is 47.

Adding to 21255216322565 its reverse (56522361255212), we get a palindrome (77777577577777).

The spelling of 21255216322565 in words is "twenty-one trillion, two hundred fifty-five billion, two hundred sixteen million, three hundred twenty-two thousand, five hundred sixty-five".