7981865 has 4 divisors (see below), whose sum is σ = 9578244. Its totient is φ = 6385488.

The previous prime is 7981859. The next prime is 7981867. The reversal of 7981865 is 5681897.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2650384 + 5331481 = 1628^2 + 2309^2 .

It is a cyclic number.

It is not a de Polignac number, because 7981865 - 2⁶ = 7981801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7981867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 798182 + ... + 798191.

It is an arithmetic number, because the mean of its divisors is an integer number (2394561).

Almost surely, 2^7981865 is an apocalyptic number.

It is an amenable number.

7981865 is a deficient number, since it is larger than the sum of its proper divisors (1596379).

7981865 is a wasteful number, since it uses less digits than its factorization.

7981865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1596378.

The product of its digits is 120960, while the sum is 44.

The square root of 7981865 is about 2825.2194605021. The cubic root of 7981865 is about 199.8487606621.

Subtracting from 7981865 its reverse (5681897), we obtain a cube (2299968 = 132³).

The spelling of 7981865 in words is "seven million, nine hundred eighty-one thousand, eight hundred sixty-five".