161616531521 has 2 divisors, whose sum is σ = 161616531522. Its totient is φ = 161616531520.

The previous prime is 161616531457. The next prime is 161616531533. The reversal of 161616531521 is 125135616161.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 155094192400 + 6522339121 = 393820^2 + 80761^2 .

It is a cyclic number.

It is not a de Polignac number, because 161616531521 - 2⁶ = 161616531457 is a prime.

It is a super-2 number, since 2×161616531521² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (161616531421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80808265760 + 80808265761.

It is an arithmetic number, because the mean of its divisors is an integer number (80808265761).

Almost surely, 2^161616531521 is an apocalyptic number.

It is an amenable number.

161616531521 is a deficient number, since it is larger than the sum of its proper divisors (1).

161616531521 is an equidigital number, since it uses as much as digits as its factorization.

161616531521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32400, while the sum is 38.

The spelling of 161616531521 in words is "one hundred sixty-one billion, six hundred sixteen million, five hundred thirty-one thousand, five hundred twenty-one".