816531 has 8 divisors (see below), whose sum is σ = 1112064. Its totient is φ = 532680.

The previous prime is 816521. The next prime is 816539. The reversal of 816531 is 135618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 816531 - 2⁵ = 816499 is a prime.

It is a super-2 number, since 2×816531² = 1333445747922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (816539) 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, 2755 + ... + 3036.

It is an arithmetic number, because the mean of its divisors is an integer number (139008).

2⁸¹⁶⁵³¹ is an apocalyptic number.

816531 is the 572-nd centered pentagonal number.

816531 is a deficient number, since it is larger than the sum of its proper divisors (295533).

816531 is a wasteful number, since it uses less digits than its factorization.

816531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5841.

The product of its digits is 720, while the sum is 24.

The square root of 816531 is about 903.6210488916. The cubic root of 816531 is about 93.4668398334.

The spelling of 816531 in words is "eight hundred sixteen thousand, five hundred thirty-one".