168538991 has 4 divisors (see below), whose sum is σ = 169165800. Its totient is φ = 167912184.

The previous prime is 168538943. The next prime is 168538999. The reversal of 168538991 is 199835861.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 168538991 - 2⁶ = 168538927 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (168538999) 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, 313001 + ... + 313538.

It is an arithmetic number, because the mean of its divisors is an integer number (42291450).

Almost surely, 2^168538991 is an apocalyptic number.

168538991 is a deficient number, since it is larger than the sum of its proper divisors (626809).

168538991 is an equidigital number, since it uses as much as digits as its factorization.

168538991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 626808.

The product of its digits is 466560, while the sum is 50.

The square root of 168538991 is about 12982.2567760771. The cubic root of 168538991 is about 552.3742987104.

The spelling of 168538991 in words is "one hundred sixty-eight million, five hundred thirty-eight thousand, nine hundred ninety-one".