161720812857 has 16 divisors (see below), whose sum is σ = 216476483328. Its totient is φ = 107389704960.

The previous prime is 161720812853. The next prime is 161720812859. The reversal of 161720812857 is 758218027161.

It is not a de Polignac number, because 161720812857 - 2² = 161720812853 is a prime.

It is a super-2 number, since 2×161720812857² (a number of 23 digits) contains 22 as substring.

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 in 15 ways as a sum of consecutive naturals, for example, 3630673 + ... + 3674945.

It is an arithmetic number, because the mean of its divisors is an integer number (13529780208).

Almost surely, 2^161720812857 is an apocalyptic number.

It is an amenable number.

161720812857 is a deficient number, since it is larger than the sum of its proper divisors (54755670471).

161720812857 is a wasteful number, since it uses less digits than its factorization.

161720812857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49040.

The product of its (nonzero) digits is 376320, while the sum is 48.

The spelling of 161720812857 in words is "one hundred sixty-one billion, seven hundred twenty million, eight hundred twelve thousand, eight hundred fifty-seven".