78430021 has 2 divisors, whose sum is σ = 78430022. Its totient is φ = 78430020.

The previous prime is 78430013. The next prime is 78430039. The reversal of 78430021 is 12003487.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76212900 + 2217121 = 8730^2 + 1489^2 .

It is a cyclic number.

It is not a de Polignac number, because 78430021 - 2³ = 78430013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78430321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39215010 + 39215011.

It is an arithmetic number, because the mean of its divisors is an integer number (39215011).

Almost surely, 2^78430021 is an apocalyptic number.

It is an amenable number.

78430021 is a deficient number, since it is larger than the sum of its proper divisors (1).

78430021 is an equidigital number, since it uses as much as digits as its factorization.

78430021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 78430021 is about 8856.0725493867. The cubic root of 78430021 is about 428.0496146664.

The spelling of 78430021 in words is "seventy-eight million, four hundred thirty thousand, twenty-one".