78231721 has 8 divisors (see below), whose sum is σ = 82536320. Its totient is φ = 73945872.

The previous prime is 78231709. The next prime is 78231779. The reversal of 78231721 is 12713287.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 78231721 - 2⁵ = 78231689 is a prime.

It is a super-2 number, since 2×78231721² = 12240404341243682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78231701) 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 7 ways as a sum of consecutive naturals, for example, 4351 + ... + 13243.

It is an arithmetic number, because the mean of its divisors is an integer number (10317040).

Almost surely, 2^78231721 is an apocalyptic number.

It is an amenable number.

78231721 is a deficient number, since it is larger than the sum of its proper divisors (4304599).

78231721 is a wasteful number, since it uses less digits than its factorization.

78231721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9375.

The product of its digits is 4704, while the sum is 31.

The square root of 78231721 is about 8844.8697559659. The cubic root of 78231721 is about 427.6885544669.

The spelling of 78231721 in words is "seventy-eight million, two hundred thirty-one thousand, seven hundred twenty-one".