21786834917 has 2 divisors, whose sum is σ = 21786834918. Its totient is φ = 21786834916.

The previous prime is 21786834869. The next prime is 21786834919. The reversal of 21786834917 is 71943868712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12145362436 + 9641472481 = 110206^2 + 98191^2 .

It is a cyclic number.

It is not a de Polignac number, because 21786834917 - 2¹⁴ = 21786818533 is a prime.

It is a super-2 number, since 2×21786834917² (a number of 21 digits) contains 22 as substring.

Together with 21786834919, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21786834919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10893417458 + 10893417459.

It is an arithmetic number, because the mean of its divisors is an integer number (10893417459).

Almost surely, 2^21786834917 is an apocalyptic number.

It is an amenable number.

21786834917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21786834917 is an equidigital number, since it uses as much as digits as its factorization.

21786834917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4064256, while the sum is 56.

The spelling of 21786834917 in words is "twenty-one billion, seven hundred eighty-six million, eight hundred thirty-four thousand, nine hundred seventeen".