21506201635609 has 2 divisors, whose sum is σ = 21506201635610. Its totient is φ = 21506201635608.

The previous prime is 21506201635517. The next prime is 21506201635613. The reversal of 21506201635609 is 90653610260512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18647153515225 + 2859048120384 = 4318235^2 + 1690872^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506201635609 - 2³³ = 21497611701017 is a prime.

It is not a weakly prime, because it can be changed into another prime (21506201635649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753100817804 + 10753100817805.

It is an arithmetic number, because the mean of its divisors is an integer number (10753100817805).

Almost surely, 2^{21506201635609} is an apocalyptic number.

It is an amenable number.

21506201635609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506201635609 is an equidigital number, since it uses as much as digits as its factorization.

21506201635609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 583200, while the sum is 46.

The spelling of 21506201635609 in words is "twenty-one trillion, five hundred six billion, two hundred one million, six hundred thirty-five thousand, six hundred nine".