820857239 has 2 divisors, whose sum is σ = 820857240. Its totient is φ = 820857238.

The previous prime is 820857221. The next prime is 820857253. The reversal of 820857239 is 932758028.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 820857239 - 2⁸ = 820856983 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 820857239.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (820857299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410428619 + 410428620.

It is an arithmetic number, because the mean of its divisors is an integer number (410428620).

Almost surely, 2^820857239 is an apocalyptic number.

820857239 is a deficient number, since it is larger than the sum of its proper divisors (1).

820857239 is an equidigital number, since it uses as much as digits as its factorization.

820857239 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 241920, while the sum is 44.

The square root of 820857239 is about 28650.6062588560. The cubic root of 820857239 is about 936.3162142780.

The spelling of 820857239 in words is "eight hundred twenty million, eight hundred fifty-seven thousand, two hundred thirty-nine".