816981 has 16 divisors (see below), whose sum is σ = 1251840. Its totient is φ = 468720.

The previous prime is 816971. The next prime is 817013. The reversal of 816981 is 189618.

It is not a de Polignac number, because 816981 - 2⁶ = 816917 is a prime.

It is a super-2 number, since 2×816981² = 1334915908722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an alternating number because its digits alternate between even and odd.

It is a nialpdrome in base 16.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 816981.

It is not an unprimeable number, because it can be changed into a prime (816911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25 + ... + 1278.

It is an arithmetic number, because the mean of its divisors is an integer number (78240).

2⁸¹⁶⁹⁸¹ is an apocalyptic number.

It is an amenable number.

816981 is a deficient number, since it is larger than the sum of its proper divisors (434859).

816981 is a wasteful number, since it uses less digits than its factorization.

816981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1336.

The product of its digits is 3456, while the sum is 33.

The square root of 816981 is about 903.8700127784. The cubic root of 816981 is about 93.4840069112.

The spelling of 816981 in words is "eight hundred sixteen thousand, nine hundred eighty-one".