815711989 has 2 divisors, whose sum is σ = 815711990. Its totient is φ = 815711988.

The previous prime is 815711927. The next prime is 815712031. The reversal of 815711989 is 989117518.

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., 597411364 + 218300625 = 24442^2 + 14775^2 .

It is a cyclic number.

It is not a de Polignac number, because 815711989 - 2¹³ = 815703797 is a prime.

It is a super-2 number, since 2×815711989² = 1330772097996672242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (815711189) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407855994 + 407855995.

It is an arithmetic number, because the mean of its divisors is an integer number (407855995).

Almost surely, 2^815711989 is an apocalyptic number.

It is an amenable number.

815711989 is a deficient number, since it is larger than the sum of its proper divisors (1).

815711989 is an equidigital number, since it uses as much as digits as its factorization.

815711989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 181440, while the sum is 49.

The square root of 815711989 is about 28560.6720684230. The cubic root of 815711989 is about 934.3557913882.

The spelling of 815711989 in words is "eight hundred fifteen million, seven hundred eleven thousand, nine hundred eighty-nine".