21604006217609 has 2 divisors, whose sum is σ = 21604006217610. Its totient is φ = 21604006217608.

The previous prime is 21604006217587. The next prime is 21604006217653. The reversal of 21604006217609 is 90671260040612.

It is an a-pointer prime, because the next prime (21604006217653) can be obtained adding 21604006217609 to its sum of digits (44).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21010736560009 + 593269657600 = 4583747^2 + 770240^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21604006217609 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21604006217609.

It is not a weakly prime, because it can be changed into another prime (21604006217659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802003108804 + 10802003108805.

It is an arithmetic number, because the mean of its divisors is an integer number (10802003108805).

Almost surely, 2^{21604006217609} is an apocalyptic number.

It is an amenable number.

21604006217609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21604006217609 is an equidigital number, since it uses as much as digits as its factorization.

21604006217609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 217728, while the sum is 44.

The spelling of 21604006217609 in words is "twenty-one trillion, six hundred four billion, six million, two hundred seventeen thousand, six hundred nine".