21645717101689 has 2 divisors, whose sum is σ = 21645717101690. Its totient is φ = 21645717101688.

The previous prime is 21645717101651. The next prime is 21645717101753. The reversal of 21645717101689 is 98610171754612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21525266458089 + 120450643600 = 4639533^2 + 347060^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21645717101689 is a prime.

It is not a weakly prime, because it can be changed into another prime (21645717101629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10822858550844 + 10822858550845.

It is an arithmetic number, because the mean of its divisors is an integer number (10822858550845).

Almost surely, 2^{21645717101689} is an apocalyptic number.

It is an amenable number.

21645717101689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21645717101689 is an equidigital number, since it uses as much as digits as its factorization.

21645717101689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5080320, while the sum is 58.

The spelling of 21645717101689 in words is "twenty-one trillion, six hundred forty-five billion, seven hundred seventeen million, one hundred one thousand, six hundred eighty-nine".