161605566661631 has 2 divisors, whose sum is σ = 161605566661632. Its totient is φ = 161605566661630.

The previous prime is 161605566661621. The next prime is 161605566661661. The reversal of 161605566661631 is 136166665506161.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 161605566661631 - 2¹⁰ = 161605566660607 is a prime.

It is a super-2 number, since 2×161605566661631² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161605566661621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80802783330815 + 80802783330816.

It is an arithmetic number, because the mean of its divisors is an integer number (80802783330816).

Almost surely, 2^{161605566661631} is an apocalyptic number.

161605566661631 is a deficient number, since it is larger than the sum of its proper divisors (1).

161605566661631 is an equidigital number, since it uses as much as digits as its factorization.

161605566661631 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20995200, while the sum is 59.

The spelling of 161605566661631 in words is "one hundred sixty-one trillion, six hundred five billion, five hundred sixty-six million, six hundred sixty-one thousand, six hundred thirty-one".