82790021 has 2 divisors, whose sum is σ = 82790022. Its totient is φ = 82790020.

The previous prime is 82790009. The next prime is 82790023. The reversal of 82790021 is 12009728.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79459396 + 3330625 = 8914^2 + 1825^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-82790021 is a prime.

It is a Sophie Germain prime.

Together with 82790023, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (82790023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41395010 + 41395011.

It is an arithmetic number, because the mean of its divisors is an integer number (41395011).

Almost surely, 2^82790021 is an apocalyptic number.

It is an amenable number.

82790021 is a deficient number, since it is larger than the sum of its proper divisors (1).

82790021 is an equidigital number, since it uses as much as digits as its factorization.

82790021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 82790021 is about 9098.9021865278. The cubic root of 82790021 is about 435.8389078162.

Adding to 82790021 its reverse (12009728), we get a palindrome (94799749).

The spelling of 82790021 in words is "eighty-two million, seven hundred ninety thousand, twenty-one".