660821 has 8 divisors (see below), whose sum is σ = 767040. Its totient is φ = 557568.

The previous prime is 660817. The next prime is 660833. The reversal of 660821 is 128066.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 660821 - 2² = 660817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (660811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 236 + ... + 1173.

It is an arithmetic number, because the mean of its divisors is an integer number (95880).

2⁶⁶⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

660821 is a deficient number, since it is larger than the sum of its proper divisors (106219).

660821 is a wasteful number, since it uses less digits than its factorization.

660821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1483.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 660821 is about 812.9089739940. The cubic root of 660821 is about 87.1019635107.

Adding to 660821 its reverse (128066), we get a palindrome (788887).

The spelling of 660821 in words is "six hundred sixty thousand, eight hundred twenty-one".