821730 has 96 divisors (see below), whose sum is σ = 2528064. Its totient is φ = 169344.

The previous prime is 821677. The next prime is 821741. The reversal of 821730 is 37128.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 821697 and 821706.

It is an unprimeable number.

821730 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 19089 + ... + 19131.

It is an arithmetic number, because the mean of its divisors is an integer number (26334).

2⁸²¹⁷³⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 821730, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1264032).

821730 is an abundant number, since it is smaller than the sum of its proper divisors (1706334).

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

821730 is a wasteful number, since it uses less digits than its factorization.

821730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80 (or 73 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 821730 is about 906.4932432181. The cubic root of 821730 is about 93.6647936933.

Adding to 821730 its reverse (37128), we get a palindrome (858858).

It can be divided in two parts, 821 and 730, that added together give a palindrome (1551).

The spelling of 821730 in words is "eight hundred twenty-one thousand, seven hundred thirty".