78720321 has 4 divisors (see below), whose sum is σ = 104960432. Its totient is φ = 52480212.

The previous prime is 78720311. The next prime is 78720359. The reversal of 78720321 is 12302787.

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.

It is not a de Polignac number, because 78720321 - 2⁵ = 78720289 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (78720311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13120051 + ... + 13120056.

It is an arithmetic number, because the mean of its divisors is an integer number (26240108).

Almost surely, 2^78720321 is an apocalyptic number.

It is an amenable number.

78720321 is a deficient number, since it is larger than the sum of its proper divisors (26240111).

78720321 is a wasteful number, since it uses less digits than its factorization.

78720321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26240110.

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 78720321 is about 8872.4472948561. The cubic root of 78720321 is about 428.5770904173.

The spelling of 78720321 in words is "seventy-eight million, seven hundred twenty thousand, three hundred twenty-one".