865943774721 has 9 divisors (see below), whose sum is σ = 1250811707041. Its totient is φ = 577293988692.

The previous prime is 865943774719. The next prime is 865943774723. The reversal of 865943774721 is 127477349568.

The square root of 865943774721 is 930561.

It is a perfect power (a square), and thus also a powerful number.

865943774721 is a `hidden beast` number, since 8 + 6 + 5 + 94 + 3 + 77 + 472 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (865943774719) and next prime (865943774723).

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 865943774721 - 2¹ = 865943774719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (865943774723) 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 in 8 ways as a sum of consecutive naturals, for example, 2636590 + ... + 2946776.

Almost surely, 2^865943774721 is an apocalyptic number.

865943774721 is the 930561-st square number.

865943774721 is the 465281-st centered octagonal number.

It is an amenable number.

865943774721 is a deficient number, since it is larger than the sum of its proper divisors (384867932320).

865943774721 is an frugal number, since it uses more digits than its factorization.

865943774721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 620380 (or 310190 counting only the distinct ones).

The product of its digits is 71124480, while the sum is 63.

The spelling of 865943774721 in words is "eight hundred sixty-five billion, nine hundred forty-three million, seven hundred seventy-four thousand, seven hundred twenty-one".