811521 has 12 divisors (see below), whose sum is σ = 1204372. Its totient is φ = 526176.

The previous prime is 811519. The next prime is 811523. The reversal of 811521 is 125118.

It is an interprime number because it is at equal distance from previous prime (811519) and next prime (811523).

It can be written as a sum of positive squares in 2 ways, for example, as 746496 + 65025 = 864^2 + 255^2 .

It is not a de Polignac number, because 811521 - 2¹ = 811519 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 811494 and 811503.

It is not an unprimeable number, because it can be changed into a prime (811523) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 886 + ... + 1551.

2⁸¹¹⁵²¹ is an apocalyptic number.

It is an amenable number.

811521 is a deficient number, since it is larger than the sum of its proper divisors (392851).

811521 is a wasteful number, since it uses less digits than its factorization.

811521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2480 (or 2477 counting only the distinct ones).

The product of its digits is 80, while the sum is 18.

The square root of 811521 is about 900.8446036914. The cubic root of 811521 is about 93.2752856173.

Adding to 811521 its reverse (125118), we get a palindrome (936639).

It can be divided in two parts, 81 and 1521, that multiplied together give a square (123201 = 351²).

The spelling of 811521 in words is "eight hundred eleven thousand, five hundred twenty-one".