21356205634345 has 4 divisors (see below), whose sum is σ = 25627446761220. Its totient is φ = 17084964507472.

The previous prime is 21356205634271. The next prime is 21356205634417. The reversal of 21356205634345 is 54343650265312.

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 10498047124761 + 10858158509584 = 3240069^2 + 3295172^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21356205634345 is a prime.

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, 2135620563430 + ... + 2135620563439.

It is an arithmetic number, because the mean of its divisors is an integer number (6406861690305).

Almost surely, 2^{21356205634345} is an apocalyptic number.

It is an amenable number.

21356205634345 is a deficient number, since it is larger than the sum of its proper divisors (4271241126875).

21356205634345 is an equidigital number, since it uses as much as digits as its factorization.

21356205634345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4271241126874.

The product of its (nonzero) digits is 7776000, while the sum is 49.

Adding to 21356205634345 its reverse (54343650265312), we get a palindrome (75699855899657).

The spelling of 21356205634345 in words is "twenty-one trillion, three hundred fifty-six billion, two hundred five million, six hundred thirty-four thousand, three hundred forty-five".