815867561 has 2 divisors, whose sum is σ = 815867562. Its totient is φ = 815867560.

The previous prime is 815867513. The next prime is 815867567. The reversal of 815867561 is 165768518.

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., 814017961 + 1849600 = 28531^2 + 1360^2 .

It is a cyclic number.

It is not a de Polignac number, because 815867561 - 2²⁶ = 748758697 is a prime.

It is not a weakly prime, because it can be changed into another prime (815867567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407933780 + 407933781.

It is an arithmetic number, because the mean of its divisors is an integer number (407933781).

Almost surely, 2^815867561 is an apocalyptic number.

It is an amenable number.

815867561 is a deficient number, since it is larger than the sum of its proper divisors (1).

815867561 is an equidigital number, since it uses as much as digits as its factorization.

815867561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 403200, while the sum is 47.

The square root of 815867561 is about 28563.3954739278. The cubic root of 815867561 is about 934.4151874991.

The spelling of 815867561 in words is "eight hundred fifteen million, eight hundred sixty-seven thousand, five hundred sixty-one".