21660551121311 has 4 divisors (see below), whose sum is σ = 21934735312800. Its totient is φ = 21386366929824.

The previous prime is 21660551121289. The next prime is 21660551121373. The reversal of 21660551121311 is 11312115506612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21660551121311 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21660551121511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 137092095626 + ... + 137092095783.

It is an arithmetic number, because the mean of its divisors is an integer number (5483683828200).

Almost surely, 2^{21660551121311} is an apocalyptic number.

21660551121311 is a deficient number, since it is larger than the sum of its proper divisors (274184191489).

21660551121311 is an equidigital number, since it uses as much as digits as its factorization.

21660551121311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274184191488.

The product of its (nonzero) digits is 10800, while the sum is 35.

Adding to 21660551121311 its reverse (11312115506612), we get a palindrome (32972666627923).

The spelling of 21660551121311 in words is "twenty-one trillion, six hundred sixty billion, five hundred fifty-one million, one hundred twenty-one thousand, three hundred eleven".