861994561 has 2 divisors, whose sum is σ = 861994562. Its totient is φ = 861994560.

The previous prime is 861994519. The next prime is 861994607. The reversal of 861994561 is 165499168.

861994561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 797497600 + 64496961 = 28240^2 + 8031^2 .

It is a cyclic number.

It is not a de Polignac number, because 861994561 - 2¹⁷ = 861863489 is a prime.

It is not a weakly prime, because it can be changed into another prime (861994961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430997280 + 430997281.

It is an arithmetic number, because the mean of its divisors is an integer number (430997281).

Almost surely, 2^861994561 is an apocalyptic number.

It is an amenable number.

861994561 is a deficient number, since it is larger than the sum of its proper divisors (1).

861994561 is an equidigital number, since it uses as much as digits as its factorization.

861994561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 466560, while the sum is 49.

The square root of 861994561 is about 29359.7438851227. The cubic root of 861994561 is about 951.7031538211.

The spelling of 861994561 in words is "eight hundred sixty-one million, nine hundred ninety-four thousand, five hundred sixty-one".