21313116551 has 4 divisors (see below), whose sum is σ = 21832948704. Its totient is φ = 20793284400.

The previous prime is 21313116523. The next prime is 21313116581. The reversal of 21313116551 is 15561131312.

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

It is a cyclic number.

It is not a de Polignac number, because 21313116551 - 2²⁶ = 21246007687 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21313116581) by changing a digit.

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, 259916015 + ... + 259916096.

It is an arithmetic number, because the mean of its divisors is an integer number (5458237176).

Almost surely, 2^21313116551 is an apocalyptic number.

21313116551 is a deficient number, since it is larger than the sum of its proper divisors (519832153).

21313116551 is an equidigital number, since it uses as much as digits as its factorization.

21313116551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 519832152.

The product of its digits is 2700, while the sum is 29.

Adding to 21313116551 its reverse (15561131312), we get a palindrome (36874247863).

The spelling of 21313116551 in words is "twenty-one billion, three hundred thirteen million, one hundred sixteen thousand, five hundred fifty-one".