1215551555161 has 2 divisors, whose sum is σ = 1215551555162. Its totient is φ = 1215551555160.

The previous prime is 1215551555111. The next prime is 1215551555189. The reversal of 1215551555161 is 1615551555121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 744346190025 + 471205365136 = 862755^2 + 686444^2 .

It is a cyclic number.

It is not a de Polignac number, because 1215551555161 - 2¹⁷ = 1215551424089 is a prime.

It is not a weakly prime, because it can be changed into another prime (1215551555111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 607775777580 + 607775777581.

It is an arithmetic number, because the mean of its divisors is an integer number (607775777581).

Almost surely, 2^{1215551555161} is an apocalyptic number.

It is an amenable number.

1215551555161 is a deficient number, since it is larger than the sum of its proper divisors (1).

1215551555161 is an equidigital number, since it uses as much as digits as its factorization.

1215551555161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 187500, while the sum is 43.

The spelling of 1215551555161 in words is "one trillion, two hundred fifteen billion, five hundred fifty-one million, five hundred fifty-five thousand, one hundred sixty-one".