21716115217 has 4 divisors (see below), whose sum is σ = 21716708020. Its totient is φ = 21715522416.

The previous prime is 21716115209. The next prime is 21716115331. The reversal of 21716115217 is 71251161712.

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 21145813056 + 570302161 = 145416^2 + 23881^2 .

It is a cyclic number.

It is not a de Polignac number, because 21716115217 - 2³ = 21716115209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21716115917) 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, 237558 + ... + 316015.

It is an arithmetic number, because the mean of its divisors is an integer number (5429177005).

Almost surely, 2^21716115217 is an apocalyptic number.

It is an amenable number.

21716115217 is a deficient number, since it is larger than the sum of its proper divisors (592803).

21716115217 is an equidigital number, since it uses as much as digits as its factorization.

21716115217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592802.

The product of its digits is 5880, while the sum is 34.

Adding to 21716115217 its reverse (71251161712), we get a palindrome (92967276929).

The spelling of 21716115217 in words is "twenty-one billion, seven hundred sixteen million, one hundred fifteen thousand, two hundred seventeen".