815989 has 2 divisors, whose sum is σ = 815990. Its totient is φ = 815988.

The previous prime is 815977. The next prime is 816019. The reversal of 815989 is 989518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 476100 + 339889 = 690^2 + 583^2 .

It is a cyclic number.

It is not a de Polignac number, because 815989 - 2¹³ = 807797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (815939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407994 + 407995.

It is an arithmetic number, because the mean of its divisors is an integer number (407995).

2⁸¹⁵⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

815989 is a deficient number, since it is larger than the sum of its proper divisors (1).

815989 is an equidigital number, since it uses as much as digits as its factorization.

815989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 40.

The square root of 815989 is about 903.3210946280. The cubic root of 815989 is about 93.4461546664.

The spelling of 815989 in words is "eight hundred fifteen thousand, nine hundred eighty-nine".