13561220809 has 2 divisors, whose sum is σ = 13561220810. Its totient is φ = 13561220808.

The previous prime is 13561220779. The next prime is 13561220857. The reversal of 13561220809 is 90802216531.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13408945209 + 152275600 = 115797^2 + 12340^2 .

It is a cyclic number.

It is not a de Polignac number, because 13561220809 - 2¹⁹ = 13560696521 is a prime.

It is a super-2 number, since 2×13561220809² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (13561220009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6780610404 + 6780610405.

It is an arithmetic number, because the mean of its divisors is an integer number (6780610405).

Almost surely, 2^13561220809 is an apocalyptic number.

It is an amenable number.

13561220809 is a deficient number, since it is larger than the sum of its proper divisors (1).

13561220809 is an equidigital number, since it uses as much as digits as its factorization.

13561220809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 37.

The spelling of 13561220809 in words is "thirteen billion, five hundred sixty-one million, two hundred twenty thousand, eight hundred nine".