78647321 has 4 divisors (see below), whose sum is σ = 83273652. Its totient is φ = 74020992.

The previous prime is 78647299. The next prime is 78647323. The reversal of 78647321 is 12374687.

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 40960000 + 37687321 = 6400^2 + 6139^2 .

It is a de Polignac number, because none of the positive numbers 2^k-78647321 is a prime.

It is a super-2 number, since 2×78647321² = 12370802200954082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78647323) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2313140 + ... + 2313173.

It is an arithmetic number, because the mean of its divisors is an integer number (20818413).

Almost surely, 2^78647321 is an apocalyptic number.

It is an amenable number.

78647321 is a deficient number, since it is larger than the sum of its proper divisors (4626331).

78647321 is a wasteful number, since it uses less digits than its factorization.

78647321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4626330.

The product of its digits is 56448, while the sum is 38.

The square root of 78647321 is about 8868.3324813631. The cubic root of 78647321 is about 428.4445714646. Note that the first 3 decimals are identical.

The spelling of 78647321 in words is "seventy-eight million, six hundred forty-seven thousand, three hundred twenty-one".