168215639881 has 3 divisors (see below), whose sum is σ = 168216050023. Its totient is φ = 168215229740.

The previous prime is 168215639873. The next prime is 168215639923. The reversal of 168215639881 is 188936512861.

It is a happy number.

The square root of 168215639881 is 410141.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 188936512861 = 251 ⋅752735111.

It can be written as a sum of positive squares in only one way, i.e., 58535447481 + 109680192400 = 241941^2 + 331180^2 .

It is not a de Polignac number, because 168215639881 - 2³ = 168215639873 is a prime.

It is a super-2 number, since 2×168215639881² (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 (168215639821) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 205071 + ... + 615211.

Almost surely, 2^168215639881 is an apocalyptic number.

168215639881 is the 410141-st square number.

168215639881 is the 205071-st centered octagonal number.

It is an amenable number.

168215639881 is a deficient number, since it is larger than the sum of its proper divisors (410142).

168215639881 is an frugal number, since it uses more digits than its factorization.

168215639881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 820282 (or 410141 counting only the distinct ones).

The product of its digits is 4976640, while the sum is 58.

The spelling of 168215639881 in words is "one hundred sixty-eight billion, two hundred fifteen million, six hundred thirty-nine thousand, eight hundred eighty-one".