809981 has 2 divisors, whose sum is σ = 809982. Its totient is φ = 809980.

The previous prime is 809929. The next prime is 809983. The reversal of 809981 is 189908.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 749956 + 60025 = 866^2 + 245^2 .

It is a cyclic number.

It is not a de Polignac number, because 809981 - 2⁶ = 809917 is a prime.

It is a super-2 number, since 2×809981² = 1312138440722, which contains 22 as substring.

Together with 809983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (809983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404990 + 404991.

It is an arithmetic number, because the mean of its divisors is an integer number (404991).

2⁸⁰⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

809981 is a deficient number, since it is larger than the sum of its proper divisors (1).

809981 is an equidigital number, since it uses as much as digits as its factorization.

809981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 35.

The square root of 809981 is about 899.9894443825. The cubic root of 809981 is about 93.2162463159.

The spelling of 809981 in words is "eight hundred nine thousand, nine hundred eighty-one".