820840720 has 80 divisors (see below), whose sum is σ = 2190574080. Its totient is φ = 280207872.

The previous prime is 820840711. The next prime is 820840729. The reversal of 820840720 is 27048028.

It is an interprime number because it is at equal distance from previous prime (820840711) and next prime (820840729).

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×820840720² = 1347558975220236800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (820840729) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 130774 + ... + 136906.

It is an arithmetic number, because the mean of its divisors is an integer number (27382176).

Almost surely, 2^820840720 is an apocalyptic number.

820840720 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 820840720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1095287040).

820840720 is an abundant number, since it is smaller than the sum of its proper divisors (1369733360).

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

820840720 is a wasteful number, since it uses less digits than its factorization.

820840720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6392 (or 6386 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 31.

The square root of 820840720 is about 28650.3179738027. The cubic root of 820840720 is about 936.3099334005.

Adding to 820840720 its reverse (27048028), we get a palindrome (847888748).

The spelling of 820840720 in words is "eight hundred twenty million, eight hundred forty thousand, seven hundred twenty".