81901 has 2 divisors, whose sum is σ = 81902.
Its totient is φ = 81900.
The previous prime is 81899. The next prime is 81919. The reversal of 81901 is 10918.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 81225 + 676 = 285^2 + 26^2
It is a cyclic number.
It is not a de Polignac number, because 81901 - 21 = 81899 is a prime.
Together with 81899, it forms a pair of twin primes.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (81931) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (13) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40950 + 40951.
It is an arithmetic number, because the mean of its divisors is an integer number (40951).
281901 is an apocalyptic number.
It is an amenable number.
81901 is a deficient number, since it is larger than the sum of its proper divisors (1).
81901 is an equidigital number, since it uses as much as digits as its factorization.
81901 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 72, while the sum is 19.
The square root of 81901 is about 286.1835075611.
The cubic root of 81901 is about 43.4273239279.
The spelling of 81901 in words is "eighty-one thousand, nine hundred one".