181993421 has 4 divisors (see below), whose sum is σ = 182073312. Its totient is φ = 181913532.

The previous prime is 181993387. The next prime is 181993423. The reversal of 181993421 is 124399181.

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 181993421 - 2²² = 177799117 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 (181993423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36425 + ... + 41118.

It is an arithmetic number, because the mean of its divisors is an integer number (45518328).

Almost surely, 2^181993421 is an apocalyptic number.

It is an amenable number.

181993421 is a deficient number, since it is larger than the sum of its proper divisors (79891).

181993421 is an equidigital number, since it uses as much as digits as its factorization.

181993421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79890.

The product of its digits is 15552, while the sum is 38.

The square root of 181993421 is about 13490.4937270657. The cubic root of 181993421 is about 566.6982822422.

The spelling of 181993421 in words is "one hundred eighty-one million, nine hundred ninety-three thousand, four hundred twenty-one".