161505611021 has 2 divisors, whose sum is σ = 161505611022. Its totient is φ = 161505611020.

The previous prime is 161505610967. The next prime is 161505611027. The reversal of 161505611021 is 120116505161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151001410921 + 10504200100 = 388589^2 + 102490^2 .

It is an emirp because it is prime and its reverse (120116505161) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161505611021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161505611027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80752805510 + 80752805511.

It is an arithmetic number, because the mean of its divisors is an integer number (80752805511).

Almost surely, 2^161505611021 is an apocalyptic number.

It is an amenable number.

161505611021 is a deficient number, since it is larger than the sum of its proper divisors (1).

161505611021 is an equidigital number, since it uses as much as digits as its factorization.

161505611021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1800, while the sum is 29.

The spelling of 161505611021 in words is "one hundred sixty-one billion, five hundred five million, six hundred eleven thousand, twenty-one".