81929 has 2 divisors, whose sum is σ = 81930. Its totient is φ = 81928.

The previous prime is 81919. The next prime is 81931. The reversal of 81929 is 92918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60025 + 21904 = 245^2 + 148^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81929 is a prime.

It is a super-2 number, since 2×81929² = 13424722082, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 81931, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (81919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40964 + 40965.

It is an arithmetic number, because the mean of its divisors is an integer number (40965).

2⁸¹⁹²⁹ is an apocalyptic number.

It is an amenable number.

81929 is a deficient number, since it is larger than the sum of its proper divisors (1).

81929 is an equidigital number, since it uses as much as digits as its factorization.

81929 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 29.

The square root of 81929 is about 286.2324230411. The cubic root of 81929 is about 43.4322722863.

It can be divided in two parts, 819 and 29, that added together give a palindrome (848).

The spelling of 81929 in words is "eighty-one thousand, nine hundred twenty-nine".