161621766617 has 4 divisors (see below), whose sum is σ = 162292396596. Its totient is φ = 160951136640.

The previous prime is 161621766599. The next prime is 161621766629. The reversal of 161621766617 is 716667126161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 716667126161 = 7 ⋅102381018023.

It can be written as a sum of positive squares in 2 ways, for example, as 67213673536 + 94408093081 = 259256^2 + 307259^2 .

It is not a de Polignac number, because 161621766617 - 2¹² = 161621762521 is a prime.

It is a super-2 number, since 2×161621766617² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161621766017) 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, 335314628 + ... + 335315109.

It is an arithmetic number, because the mean of its divisors is an integer number (40573099149).

Almost surely, 2^161621766617 is an apocalyptic number.

It is an amenable number.

161621766617 is a deficient number, since it is larger than the sum of its proper divisors (670629979).

161621766617 is an equidigital number, since it uses as much as digits as its factorization.

161621766617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 670629978.

The product of its digits is 762048, while the sum is 50.

The spelling of 161621766617 in words is "one hundred sixty-one billion, six hundred twenty-one million, seven hundred sixty-six thousand, six hundred seventeen".