215561105509 has 2 divisors, whose sum is σ = 215561105510. Its totient is φ = 215561105508.

The previous prime is 215561105491. The next prime is 215561105579. The reversal of 215561105509 is 905501165512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 179326840900 + 36234264609 = 423470^2 + 190353^2 .

It is a cyclic number.

It is not a de Polignac number, because 215561105509 - 2⁷ = 215561105381 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215561105579) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107780552754 + 107780552755.

It is an arithmetic number, because the mean of its divisors is an integer number (107780552755).

Almost surely, 2^215561105509 is an apocalyptic number.

It is an amenable number.

215561105509 is a deficient number, since it is larger than the sum of its proper divisors (1).

215561105509 is an equidigital number, since it uses as much as digits as its factorization.

215561105509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 67500, while the sum is 40.

The spelling of 215561105509 in words is "two hundred fifteen billion, five hundred sixty-one million, one hundred five thousand, five hundred nine".