820781840 has 40 divisors (see below), whose sum is σ = 1939613208. Its totient is φ = 322928640.

The previous prime is 820781827. The next prime is 820781891. The reversal of 820781840 is 48187028.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 17172736 + 803609104 = 4144^2 + 28348^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 820781794 and 820781803.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79217 + ... + 88976.

Almost surely, 2^820781840 is an apocalyptic number.

820781840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

820781840 is an abundant number, since it is smaller than the sum of its proper divisors (1118831368).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

820781840 is a wasteful number, since it uses less digits than its factorization.

820781840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168267 (or 168261 counting only the distinct ones).

The product of its (nonzero) digits is 28672, while the sum is 38.

The square root of 820781840 is about 28649.2903926083. The cubic root of 820781840 is about 936.2875452783.

The spelling of 820781840 in words is "eight hundred twenty million, seven hundred eighty-one thousand, eight hundred forty".