181391997 has 4 divisors (see below), whose sum is σ = 241856000. Its totient is φ = 120927996.

The previous prime is 181391971. The next prime is 181391999. The reversal of 181391997 is 799193181.

It is a happy number.

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 not a de Polignac number, because 181391997 - 2⁸ = 181391741 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 (181391999) 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, 30231997 + ... + 30232002.

It is an arithmetic number, because the mean of its divisors is an integer number (60464000).

Almost surely, 2^181391997 is an apocalyptic number.

It is an amenable number.

181391997 is a deficient number, since it is larger than the sum of its proper divisors (60464003).

181391997 is an equidigital number, since it uses as much as digits as its factorization.

181391997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60464002.

The product of its digits is 122472, while the sum is 48.

The square root of 181391997 is about 13468.1846215442. The cubic root of 181391997 is about 566.0733474266.

The spelling of 181391997 in words is "one hundred eighty-one million, three hundred ninety-one thousand, nine hundred ninety-seven".