78012721 has 2 divisors, whose sum is σ = 78012722. Its totient is φ = 78012720.

The previous prime is 78012719. The next prime is 78012731. The reversal of 78012721 is 12721087.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39125025 + 38887696 = 6255^2 + 6236^2 .

It is an emirp because it is prime and its reverse (12721087) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78012721 - 2¹ = 78012719 is a prime.

Together with 78012719, it forms a pair of twin primes.

It is equal to p_4560256 and since 78012721 and 4560256 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 78012721.

It is not a weakly prime, because it can be changed into another prime (78012731) 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 as a sum of consecutive naturals, namely, 39006360 + 39006361.

It is an arithmetic number, because the mean of its divisors is an integer number (39006361).

Almost surely, 2^78012721 is an apocalyptic number.

It is an amenable number.

78012721 is a deficient number, since it is larger than the sum of its proper divisors (1).

78012721 is an equidigital number, since it uses as much as digits as its factorization.

78012721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1568, while the sum is 28.

The square root of 78012721 is about 8832.4810217741. The cubic root of 78012721 is about 427.2890944675.

The spelling of 78012721 in words is "seventy-eight million, twelve thousand, seven hundred twenty-one".