78721393 has 2 divisors, whose sum is σ = 78721394. Its totient is φ = 78721392.

The previous prime is 78721361. The next prime is 78721421. The reversal of 78721393 is 39312787.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73667889 + 5053504 = 8583^2 + 2248^2 .

It is an emirp because it is prime and its reverse (39312787) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78721393 - 2⁵ = 78721361 is a prime.

It is not a weakly prime, because it can be changed into another prime (78721333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39360696 + 39360697.

It is an arithmetic number, because the mean of its divisors is an integer number (39360697).

Almost surely, 2^78721393 is an apocalyptic number.

It is an amenable number.

78721393 is a deficient number, since it is larger than the sum of its proper divisors (1).

78721393 is an equidigital number, since it uses as much as digits as its factorization.

78721393 is an evil number, because the sum of its binary digits is even.

The product of its digits is 63504, while the sum is 40.

The square root of 78721393 is about 8872.5077063928. The cubic root of 78721393 is about 428.5790358385.

The spelling of 78721393 in words is "seventy-eight million, seven hundred twenty-one thousand, three hundred ninety-three".