81438191 has 2 divisors, whose sum is σ = 81438192. Its totient is φ = 81438190.

The previous prime is 81438179. The next prime is 81438229. The reversal of 81438191 is 19183418.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81438191 - 2⁶ = 81438127 is a prime.

It is a plaindrome in base 12.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81438391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40719095 + 40719096.

It is an arithmetic number, because the mean of its divisors is an integer number (40719096).

Almost surely, 2^81438191 is an apocalyptic number.

81438191 is a deficient number, since it is larger than the sum of its proper divisors (1).

81438191 is an equidigital number, since it uses as much as digits as its factorization.

81438191 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6912, while the sum is 35.

The square root of 81438191 is about 9024.3111094421. The cubic root of 81438191 is about 433.4536915510.

The spelling of 81438191 in words is "eighty-one million, four hundred thirty-eight thousand, one hundred ninety-one".