861657817 has 2 divisors, whose sum is σ = 861657818. Its totient is φ = 861657816.

The previous prime is 861657791. The next prime is 861657851. The reversal of 861657817 is 718756168.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 751911241 + 109746576 = 27421^2 + 10476^2 .

It is a cyclic number.

It is not a de Polignac number, because 861657817 - 2¹⁵ = 861625049 is a prime.

It is not a weakly prime, because it can be changed into another prime (861657877) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430828908 + 430828909.

It is an arithmetic number, because the mean of its divisors is an integer number (430828909).

Almost surely, 2^861657817 is an apocalyptic number.

It is an amenable number.

861657817 is a deficient number, since it is larger than the sum of its proper divisors (1).

861657817 is an equidigital number, since it uses as much as digits as its factorization.

861657817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 564480, while the sum is 49.

The square root of 861657817 is about 29354.0085337591. The cubic root of 861657817 is about 951.5792079236.

The spelling of 861657817 in words is "eight hundred sixty-one million, six hundred fifty-seven thousand, eight hundred seventeen".