21026109217 has 2 divisors, whose sum is σ = 21026109218. Its totient is φ = 21026109216.

The previous prime is 21026109191. The next prime is 21026109229. The reversal of 21026109217 is 71290162012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12219975936 + 8806133281 = 110544^2 + 93841^2 .

It is a cyclic number.

It is not a de Polignac number, because 21026109217 - 2³¹ = 18878625569 is a prime.

It is not a weakly prime, because it can be changed into another prime (21026109017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10513054608 + 10513054609.

It is an arithmetic number, because the mean of its divisors is an integer number (10513054609).

Almost surely, 2^21026109217 is an apocalyptic number.

It is an amenable number.

21026109217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026109217 is an equidigital number, since it uses as much as digits as its factorization.

21026109217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 31.

The spelling of 21026109217 in words is "twenty-one billion, twenty-six million, one hundred nine thousand, two hundred seventeen".