823990821 has 4 divisors (see below), whose sum is σ = 1098654432. Its totient is φ = 549327212.

The previous prime is 823990789. The next prime is 823990823. The reversal of 823990821 is 128099328.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 823990821 - 2⁵ = 823990789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (823990823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 137331801 + ... + 137331806.

It is an arithmetic number, because the mean of its divisors is an integer number (274663608).

Almost surely, 2^823990821 is an apocalyptic number.

It is an amenable number.

823990821 is a deficient number, since it is larger than the sum of its proper divisors (274663611).

823990821 is a wasteful number, since it uses less digits than its factorization.

823990821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 274663610.

The product of its (nonzero) digits is 62208, while the sum is 42.

The square root of 823990821 is about 28705.2403055609. The cubic root of 823990821 is about 937.5061483686.

The spelling of 823990821 in words is "eight hundred twenty-three million, nine hundred ninety thousand, eight hundred twenty-one".