21311031517 has 8 divisors (see below), whose sum is σ = 21457562040. Its totient is φ = 21164966400.

The previous prime is 21311031491. The next prime is 21311031523. The reversal of 21311031517 is 71513011312.

It can be written as a sum of positive squares in 4 ways, for example, as 11975800356 + 9335231161 = 109434^2 + 96619^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21311031517 is a prime.

It is a super-3 number, since 3×21311031517³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21311031491 and 21311031500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311031527) 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 7 ways as a sum of consecutive naturals, for example, 24208 + ... + 207865.

It is an arithmetic number, because the mean of its divisors is an integer number (2682195255).

Almost surely, 2^21311031517 is an apocalyptic number.

It is an amenable number.

21311031517 is a deficient number, since it is larger than the sum of its proper divisors (146530523).

21311031517 is a wasteful number, since it uses less digits than its factorization.

21311031517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232703.

The product of its (nonzero) digits is 630, while the sum is 25.

Adding to 21311031517 its reverse (71513011312), we get a palindrome (92824042829).

The spelling of 21311031517 in words is "twenty-one billion, three hundred eleven million, thirty-one thousand, five hundred seventeen".