161720812856 has 8 divisors (see below), whose sum is σ = 303226524120. Its totient is φ = 80860406424.

The previous prime is 161720812853. The next prime is 161720812859. The reversal of 161720812856 is 658218027161.

It is an interprime number because it is at equal distance from previous prime (161720812853) and next prime (161720812859).

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 161720812856.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161720812853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10107550796 + ... + 10107550811.

It is an arithmetic number, because the mean of its divisors is an integer number (37903315515).

Almost surely, 2^161720812856 is an apocalyptic number.

It is an amenable number.

161720812856 is a deficient number, since it is larger than the sum of its proper divisors (141505711264).

161720812856 is a wasteful number, since it uses less digits than its factorization.

161720812856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20215101613 (or 20215101609 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 47.

The spelling of 161720812856 in words is "one hundred sixty-one billion, seven hundred twenty million, eight hundred twelve thousand, eight hundred fifty-six".