820857813 has 4 divisors (see below), whose sum is σ = 1094477088. Its totient is φ = 547238540.

The previous prime is 820857811. The next prime is 820857853. The reversal of 820857813 is 318758028.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 820857813 - 2¹ = 820857811 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820857811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136809633 + ... + 136809638.

It is an arithmetic number, because the mean of its divisors is an integer number (273619272).

Almost surely, 2^820857813 is an apocalyptic number.

It is an amenable number.

820857813 is a deficient number, since it is larger than the sum of its proper divisors (273619275).

820857813 is a wasteful number, since it uses less digits than its factorization.

820857813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 273619274.

The product of its (nonzero) digits is 107520, while the sum is 42.

The square root of 820857813 is about 28650.6162760943. The cubic root of 820857813 is about 936.3164325236.

It can be divided in two parts, 82085 and 7813, that added together give a palindrome (89898).

The spelling of 820857813 in words is "eight hundred twenty million, eight hundred fifty-seven thousand, eight hundred thirteen".