21697710817 has 2 divisors, whose sum is σ = 21697710818. Its totient is φ = 21697710816.

The previous prime is 21697710781. The next prime is 21697710851. The reversal of 21697710817 is 71801779612.

Together with previous prime (21697710781) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20179907136 + 1517803681 = 142056^2 + 38959^2 .

It is a cyclic number.

It is not a de Polignac number, because 21697710817 - 2¹⁵ = 21697678049 is a prime.

It is not a weakly prime, because it can be changed into another prime (21697710857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10848855408 + 10848855409.

It is an arithmetic number, because the mean of its divisors is an integer number (10848855409).

Almost surely, 2^21697710817 is an apocalyptic number.

It is an amenable number.

21697710817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21697710817 is an equidigital number, since it uses as much as digits as its factorization.

21697710817 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 296352, while the sum is 49.

The spelling of 21697710817 in words is "twenty-one billion, six hundred ninety-seven million, seven hundred ten thousand, eight hundred seventeen".