21705297169 has 2 divisors, whose sum is σ = 21705297170. Its totient is φ = 21705297168.

The previous prime is 21705297149. The next prime is 21705297191. The reversal of 21705297169 is 96179250712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19931792400 + 1773504769 = 141180^2 + 42113^2 .

It is a cyclic number.

It is not a de Polignac number, because 21705297169 - 2¹⁵ = 21705264401 is a prime.

It is a super-2 number, since 2×21705297169² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21705297149) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10852648584 + 10852648585.

It is an arithmetic number, because the mean of its divisors is an integer number (10852648585).

Almost surely, 2^21705297169 is an apocalyptic number.

It is an amenable number.

21705297169 is a deficient number, since it is larger than the sum of its proper divisors (1).

21705297169 is an equidigital number, since it uses as much as digits as its factorization.

21705297169 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 476280, while the sum is 49.

The spelling of 21705297169 in words is "twenty-one billion, seven hundred five million, two hundred ninety-seven thousand, one hundred sixty-nine".