78585721 has 4 divisors (see below), whose sum is σ = 79185744. Its totient is φ = 77985700.

The previous prime is 78585719. The next prime is 78585757. The reversal of 78585721 is 12758587.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12758587 = 2269 ⋅5623.

It is a cyclic number.

It is not a de Polignac number, because 78585721 - 2¹ = 78585719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78585761) 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 3 ways as a sum of consecutive naturals, for example, 299815 + ... + 300076.

It is an arithmetic number, because the mean of its divisors is an integer number (19796436).

Almost surely, 2^78585721 is an apocalyptic number.

It is an amenable number.

78585721 is a deficient number, since it is larger than the sum of its proper divisors (600023).

78585721 is a wasteful number, since it uses less digits than its factorization.

78585721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 600022.

The product of its digits is 156800, while the sum is 43.

The square root of 78585721 is about 8864.8587693206. The cubic root of 78585721 is about 428.3326834445.

The spelling of 78585721 in words is "seventy-eight million, five hundred eighty-five thousand, seven hundred twenty-one".