7921789 has 4 divisors (see below), whose sum is σ = 7929180. Its totient is φ = 7914400.

The previous prime is 7921787. The next prime is 7921817. The reversal of 7921789 is 9871297.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 9871297 = 997 ⋅9901.

It can be written as a sum of positive squares in 2 ways, for example, as 550564 + 7371225 = 742^2 + 2715^2 .

It is a cyclic number.

It is not a de Polignac number, because 7921789 - 2¹ = 7921787 is a prime.

It is a d-powerful number, because it can be written as 7² + 9³ + 2²¹ + 1 + 7⁸ + 8 + 9⁵ .

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7921787) 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, 1744 + ... + 4345.

It is an arithmetic number, because the mean of its divisors is an integer number (1982295).

Almost surely, 2^7921789 is an apocalyptic number.

It is an amenable number.

7921789 is a deficient number, since it is larger than the sum of its proper divisors (7391).

7921789 is a wasteful number, since it uses less digits than its factorization.

7921789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7390.

The product of its digits is 63504, while the sum is 43.

The square root of 7921789 is about 2814.5672846816. The cubic root of 7921789 is about 199.3461061105.

The spelling of 7921789 in words is "seven million, nine hundred twenty-one thousand, seven hundred eighty-nine".