82139821 has 2 divisors, whose sum is σ = 82139822. Its totient is φ = 82139820.

The previous prime is 82139747. The next prime is 82139833. The reversal of 82139821 is 12893128.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62015625 + 20124196 = 7875^2 + 4486^2 .

It is a cyclic number.

It is not a de Polignac number, because 82139821 - 2²³ = 73751213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (82137821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41069910 + 41069911.

It is an arithmetic number, because the mean of its divisors is an integer number (41069911).

Almost surely, 2^82139821 is an apocalyptic number.

It is an amenable number.

82139821 is a deficient number, since it is larger than the sum of its proper divisors (1).

82139821 is an equidigital number, since it uses as much as digits as its factorization.

82139821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6912, while the sum is 34.

The square root of 82139821 is about 9063.1021730972. The cubic root of 82139821 is about 434.6949391506.

The spelling of 82139821 in words is "eighty-two million, one hundred thirty-nine thousand, eight hundred twenty-one".