161645766409 has 4 divisors (see below), whose sum is σ = 161680362516. Its totient is φ = 161611170304.

The previous prime is 161645766343. The next prime is 161645766439. The reversal of 161645766409 is 904667546161.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 156873029184 + 4772737225 = 396072^2 + 69085^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161645766409 is a prime.

It is a super-2 number, since 2×161645766409² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 161645766409.

It is not an unprimeable number, because it can be changed into a prime (161645766439) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17291044 + ... + 17300389.

It is an arithmetic number, because the mean of its divisors is an integer number (40420090629).

Almost surely, 2^161645766409 is an apocalyptic number.

It is an amenable number.

161645766409 is a deficient number, since it is larger than the sum of its proper divisors (34596107).

161645766409 is an equidigital number, since it uses as much as digits as its factorization.

161645766409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34596106.

The product of its (nonzero) digits is 6531840, while the sum is 55.

The spelling of 161645766409 in words is "one hundred sixty-one billion, six hundred forty-five million, seven hundred sixty-six thousand, four hundred nine".