168939681 has 4 divisors (see below), whose sum is σ = 225252912. Its totient is φ = 112626452.

The previous prime is 168939649. The next prime is 168939709. The reversal of 168939681 is 186939861.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 168939681 - 2⁵ = 168939649 is a prime.

It is a super-2 number, since 2×168939681² = 57081231632763522, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (168949681) 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, 28156611 + ... + 28156616.

It is an arithmetic number, because the mean of its divisors is an integer number (56313228).

Almost surely, 2^168939681 is an apocalyptic number.

It is an amenable number.

168939681 is a deficient number, since it is larger than the sum of its proper divisors (56313231).

168939681 is an equidigital number, since it uses as much as digits as its factorization.

168939681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56313230.

The product of its digits is 559872, while the sum is 51.

The square root of 168939681 is about 12997.6798314161. The cubic root of 168939681 is about 552.8116963872.

The spelling of 168939681 in words is "one hundred sixty-eight million, nine hundred thirty-nine thousand, six hundred eighty-one".