161721566211 has 16 divisors (see below), whose sum is σ = 217430416800. Its totient is φ = 106915910400.

The previous prime is 161721566197. The next prime is 161721566221. The reversal of 161721566211 is 112665127161.

It is not a de Polignac number, because 161721566211 - 2¹⁸ = 161721304067 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 161721566211.

It is not an unprimeable number, because it can be changed into a prime (161721566221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21090 + ... + 569111.

It is an arithmetic number, because the mean of its divisors is an integer number (13589401050).

Almost surely, 2^161721566211 is an apocalyptic number.

161721566211 is a deficient number, since it is larger than the sum of its proper divisors (55708850589).

161721566211 is a wasteful number, since it uses less digits than its factorization.

161721566211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 590966.

The product of its digits is 30240, while the sum is 39.

The spelling of 161721566211 in words is "one hundred sixty-one billion, seven hundred twenty-one million, five hundred sixty-six thousand, two hundred eleven".