851021 has 4 divisors (see below), whose sum is σ = 867132. Its totient is φ = 834912.

The previous prime is 851017. The next prime is 851033. The reversal of 851021 is 120158.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 504100 + 346921 = 710^2 + 589^2 .

It is a cyclic number.

It is not a de Polignac number, because 851021 - 2² = 851017 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 (851041) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7976 + ... + 8081.

It is an arithmetic number, because the mean of its divisors is an integer number (216783).

2⁸⁵¹⁰²¹ is an apocalyptic number.

It is an amenable number.

851021 is a deficient number, since it is larger than the sum of its proper divisors (16111).

851021 is a wasteful number, since it uses less digits than its factorization.

851021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16110.

The product of its (nonzero) digits is 80, while the sum is 17.

The square root of 851021 is about 922.5079945453. The cubic root of 851021 is about 94.7647364200.

Adding to 851021 its reverse (120158), we get a palindrome (971179).

The spelling of 851021 in words is "eight hundred fifty-one thousand, twenty-one".