168405259681 has 4 divisors (see below), whose sum is σ = 170297453700. Its totient is φ = 166513065664.

The previous prime is 168405259679. The next prime is 168405259697. The reversal of 168405259681 is 186952504861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 186952504861 = 19 ⋅9839605519.

It can be written as a sum of positive squares in 2 ways, for example, as 30826580625 + 137578679056 = 175575^2 + 370916^2 .

It is a cyclic number.

It is not a de Polignac number, because 168405259681 - 2¹ = 168405259679 is a prime.

It is a super-2 number, since 2×168405259681² (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 (168405259481) 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, 946096876 + ... + 946097053.

It is an arithmetic number, because the mean of its divisors is an integer number (42574363425).

Almost surely, 2^168405259681 is an apocalyptic number.

It is an amenable number.

168405259681 is a deficient number, since it is larger than the sum of its proper divisors (1892194019).

168405259681 is an equidigital number, since it uses as much as digits as its factorization.

168405259681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1892194018.

The product of its (nonzero) digits is 4147200, while the sum is 55.

The spelling of 168405259681 in words is "one hundred sixty-eight billion, four hundred five million, two hundred fifty-nine thousand, six hundred eighty-one".