865772721 has 24 divisors (see below), whose sum is σ = 1376781120. Its totient is φ = 519890400.

The previous prime is 865772689. The next prime is 865772729. The reversal of 865772721 is 127277568.

865772721 is a `hidden beast` number, since 8 + 6 + 577 + 2 + 72 + 1 = 666.

865772721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 865772721 - 2⁵ = 865772689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (865772729) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 29325 + ... + 50906.

It is an arithmetic number, because the mean of its divisors is an integer number (57365880).

Almost surely, 2^865772721 is an apocalyptic number.

It is an amenable number.

865772721 is a deficient number, since it is larger than the sum of its proper divisors (511008399).

865772721 is a wasteful number, since it uses less digits than its factorization.

865772721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80357 (or 80354 counting only the distinct ones).

The product of its digits is 329280, while the sum is 45.

The square root of 865772721 is about 29424.0160583154. The cubic root of 865772721 is about 953.0915795158.

It can be divided in two parts, 86577 and 2721, that added together give a palindrome (89298).

The spelling of 865772721 in words is "eight hundred sixty-five million, seven hundred seventy-two thousand, seven hundred twenty-one".