147991 has 4 divisors (see below), whose sum is σ = 155800. Its totient is φ = 140184.

The previous prime is 147977. The next prime is 147997. The reversal of 147991 is 199741.

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 147991 - 2⁷ = 147863 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (147997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3876 + ... + 3913.

It is an arithmetic number, because the mean of its divisors is an integer number (38950).

2¹⁴⁷⁹⁹¹ is an apocalyptic number.

147991 is a deficient number, since it is larger than the sum of its proper divisors (7809).

147991 is an equidigital number, since it uses as much as digits as its factorization.

147991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7808.

The product of its digits is 2268, while the sum is 31.

The square root of 147991 is about 384.6959838626. The cubic root of 147991 is about 52.8946524946.

The spelling of 147991 in words is "one hundred forty-seven thousand, nine hundred ninety-one".