990821 has 8 divisors (see below), whose sum is σ = 1075200. Its totient is φ = 907632.

The previous prime is 990809. The next prime is 990841. The reversal of 990821 is 128099.

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 990821 - 2¹⁰ = 989797 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (990841) 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, 2396 + ... + 2778.

It is an arithmetic number, because the mean of its divisors is an integer number (134400).

2⁹⁹⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

990821 is a deficient number, since it is larger than the sum of its proper divisors (84379).

990821 is a wasteful number, since it uses less digits than its factorization.

990821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 595.

The product of its (nonzero) digits is 1296, while the sum is 29.

The square root of 990821 is about 995.3999196303. The cubic root of 990821 is about 99.6930923740.

The spelling of 990821 in words is "nine hundred ninety thousand, eight hundred twenty-one".