820378821 has 4 divisors (see below), whose sum is σ = 1093838432. Its totient is φ = 546919212.

The previous prime is 820378817. The next prime is 820378841. The reversal of 820378821 is 128873028.

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 not a de Polignac number, because 820378821 - 2² = 820378817 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 820378821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820378841) 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, 136729801 + ... + 136729806.

It is an arithmetic number, because the mean of its divisors is an integer number (273459608).

Almost surely, 2^820378821 is an apocalyptic number.

It is an amenable number.

820378821 is a deficient number, since it is larger than the sum of its proper divisors (273459611).

820378821 is a wasteful number, since it uses less digits than its factorization.

820378821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 273459610.

The product of its (nonzero) digits is 43008, while the sum is 39.

The square root of 820378821 is about 28642.2558643693. The cubic root of 820378821 is about 936.1342753799.

The spelling of 820378821 in words is "eight hundred twenty million, three hundred seventy-eight thousand, eight hundred twenty-one".