816021 has 8 divisors (see below), whose sum is σ = 1208960. Its totient is φ = 543996.

The previous prime is 816019. The next prime is 816037. The reversal of 816021 is 120618.

It is not a de Polignac number, because 816021 - 2¹ = 816019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 815985 and 816003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15085 + ... + 15138.

It is an arithmetic number, because the mean of its divisors is an integer number (151120).

2⁸¹⁶⁰²¹ is an apocalyptic number.

It is an amenable number.

816021 is a deficient number, since it is larger than the sum of its proper divisors (392939).

816021 is a wasteful number, since it uses less digits than its factorization.

816021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30232 (or 30226 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 816021 is about 903.3388068715. The cubic root of 816021 is about 93.4473761853.

Subtracting from 816021 its sum of digits (18), we obtain a triangular number (816003 = T₁₂₇₇).

Adding to 816021 its reverse (120618), we get a palindrome (936639).

The spelling of 816021 in words is "eight hundred sixteen thousand, twenty-one".