161491720605 has 16 divisors (see below), whose sum is σ = 261657473280. Its totient is φ = 85038677568.

The previous prime is 161491720591. The next prime is 161491720651. The reversal of 161491720605 is 506027194161.

It is not a de Polignac number, because 161491720605 - 2⁸ = 161491720349 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 68138782 + ... + 68141151.

It is an arithmetic number, because the mean of its divisors is an integer number (16353592080).

Almost surely, 2^161491720605 is an apocalyptic number.

161491720605 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

161491720605 is a deficient number, since it is larger than the sum of its proper divisors (100165752675).

161491720605 is a wasteful number, since it uses less digits than its factorization.

161491720605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136280020.

The product of its (nonzero) digits is 90720, while the sum is 42.

The spelling of 161491720605 in words is "one hundred sixty-one billion, four hundred ninety-one million, seven hundred twenty thousand, six hundred five".