690821 has 8 divisors (see below), whose sum is σ = 736320. Its totient is φ = 646272.

The previous prime is 690817. The next prime is 690839. The reversal of 690821 is 128096.

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 690821 - 2² = 690817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 690821.

It is not an unprimeable number, because it can be changed into a prime (690841) 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, 1781 + ... + 2133.

It is an arithmetic number, because the mean of its divisors is an integer number (92040).

2⁶⁹⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

690821 is a deficient number, since it is larger than the sum of its proper divisors (45499).

690821 is a wasteful number, since it uses less digits than its factorization.

690821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 475.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 690821 is about 831.1564233043. The cubic root of 690821 is about 88.4005927357.

The spelling of 690821 in words is "six hundred ninety thousand, eight hundred twenty-one".