820428187709 has 12 divisors (see below), whose sum is σ = 888421316436. Its totient is φ = 757293892992.

The previous prime is 820428187703. The next prime is 820428187721. The reversal of 820428187709 is 907781824028.

820428187709 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 6 ways, for example, as 26057062084 + 794371125625 = 161422^2 + 891275^2 .

It is not a de Polignac number, because 820428187709 - 2²⁴ = 820411410493 is a prime.

It is a super-2 number, since 2×820428187709² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820428187703) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7135097 + ... + 7249169.

It is an arithmetic number, because the mean of its divisors is an integer number (74035109703).

Almost surely, 2^820428187709 is an apocalyptic number.

It is an amenable number.

820428187709 is a deficient number, since it is larger than the sum of its proper divisors (67993128727).

820428187709 is a wasteful number, since it uses less digits than its factorization.

820428187709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156656 (or 156643 counting only the distinct ones).

The product of its (nonzero) digits is 3612672, while the sum is 56.

The spelling of 820428187709 in words is "eight hundred twenty billion, four hundred twenty-eight million, one hundred eighty-seven thousand, seven hundred nine".