81919 has 2 divisors, whose sum is σ = 81920.
Its totient is φ = 81918.
The previous prime is 81901. The next prime is 81929. The reversal of 81919 is 91918.
Subtracting 81919 from its reverse (91918), we obtain a palindrome (9999).
It can be divided in two parts, 819 and 19, that added together give a palindrome (838).
It is a strong prime.
It is a cyclic number.
It is not a de Polignac number, because 81919 - 213 = 73727 is a prime.
It is a super-2 number, since 2×819192 = 13421445122, which contains 22 as substring.
It is a plaindrome in base 8 and base 16.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (81929) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40959 + 40960.
It is an arithmetic number, because the mean of its divisors is an integer number (40960).
281919 is an apocalyptic number.
81919 is a deficient number, since it is larger than the sum of its proper divisors (1).
81919 is an equidigital number, since it uses as much as digits as its factorization.
81919 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 648, while the sum is 28.
The square root of 81919 is about 286.2149541865.
The cubic root of 81919 is about 43.4305051449.
The spelling of 81919 in words is "eighty-one thousand, nine hundred nineteen".