78865421 has 2 divisors, whose sum is σ = 78865422. Its totient is φ = 78865420.

The previous prime is 78865417. The next prime is 78865429. The reversal of 78865421 is 12456887.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78517321 + 348100 = 8861^2 + 590^2 .

It is an emirp because it is prime and its reverse (12456887) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78865421 - 2² = 78865417 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78865429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39432710 + 39432711.

It is an arithmetic number, because the mean of its divisors is an integer number (39432711).

Almost surely, 2^78865421 is an apocalyptic number.

It is an amenable number.

78865421 is a deficient number, since it is larger than the sum of its proper divisors (1).

78865421 is an equidigital number, since it uses as much as digits as its factorization.

78865421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 107520, while the sum is 41.

The square root of 78865421 is about 8880.6205301206. The cubic root of 78865421 is about 428.8402514664.

The spelling of 78865421 in words is "seventy-eight million, eight hundred sixty-five thousand, four hundred twenty-one".