161721499173 has 96 divisors (see below), whose sum is σ = 247082887296. Its totient is φ = 93476477952.

The previous prime is 161721499141. The next prime is 161721499193. The reversal of 161721499173 is 371994127161.

It is a happy number.

It is not a de Polignac number, because 161721499173 - 2⁵ = 161721499141 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161721499193) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 189591015 + ... + 189591867.

It is an arithmetic number, because the mean of its divisors is an integer number (2573780076).

Almost surely, 2^161721499173 is an apocalyptic number.

161721499173 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

161721499173 is a deficient number, since it is larger than the sum of its proper divisors (85361388123).

161721499173 is a wasteful number, since it uses less digits than its factorization.

161721499173 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1063 (or 1026 counting only the distinct ones).

The product of its digits is 571536, while the sum is 51.

The spelling of 161721499173 in words is "one hundred sixty-one billion, seven hundred twenty-one million, four hundred ninety-nine thousand, one hundred seventy-three".