155561165909 has 2 divisors, whose sum is σ = 155561165910. Its totient is φ = 155561165908.

The previous prime is 155561165887. The next prime is 155561165959. The reversal of 155561165909 is 909561165551.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 151122675025 + 4438490884 = 388745^2 + 66622^2 .

It is a cyclic number.

It is not a de Polignac number, because 155561165909 - 2²⁴ = 155544388693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155561165959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77780582954 + 77780582955.

It is an arithmetic number, because the mean of its divisors is an integer number (77780582955).

Almost surely, 2^155561165909 is an apocalyptic number.

It is an amenable number.

155561165909 is a deficient number, since it is larger than the sum of its proper divisors (1).

155561165909 is an equidigital number, since it uses as much as digits as its factorization.

155561165909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1822500, while the sum is 53.

The spelling of 155561165909 in words is "one hundred fifty-five billion, five hundred sixty-one million, one hundred sixty-five thousand, nine hundred nine".