82106721 has 6 divisors (see below), whose sum is σ = 118598610. Its totient is φ = 54737808.

The previous prime is 82106707. The next prime is 82106729. The reversal of 82106721 is 12760128.

It can be written as a sum of positive squares in only one way, i.e., 71216721 + 10890000 = 8439^2 + 3300^2 .

It is not a de Polignac number, because 82106721 - 2¹⁸ = 81844577 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (82106729) 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 in 5 ways as a sum of consecutive naturals, for example, 4561476 + ... + 4561493.

It is an arithmetic number, because the mean of its divisors is an integer number (19766435).

Almost surely, 2^82106721 is an apocalyptic number.

It is an amenable number.

82106721 is a deficient number, since it is larger than the sum of its proper divisors (36491889).

82106721 is a wasteful number, since it uses less digits than its factorization.

82106721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9122975 (or 9122972 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 82106721 is about 9061.2759035359. The cubic root of 82106721 is about 434.6365414273.

Adding to 82106721 its reverse (12760128), we get a palindrome (94866849).

The spelling of 82106721 in words is "eighty-two million, one hundred six thousand, seven hundred twenty-one".