78724421 has 4 divisors (see below), whose sum is σ = 79672992. Its totient is φ = 77775852.

The previous prime is 78724417. The next prime is 78724453. The reversal of 78724421 is 12442787.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12442787 = 7 ⋅1777541.

It is a cyclic number.

It is not a de Polignac number, because 78724421 - 2² = 78724417 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78724411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 474161 + ... + 474326.

It is an arithmetic number, because the mean of its divisors is an integer number (19918248).

Almost surely, 2^78724421 is an apocalyptic number.

It is an amenable number.

78724421 is a deficient number, since it is larger than the sum of its proper divisors (948571).

78724421 is an equidigital number, since it uses as much as digits as its factorization.

78724421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 948570.

The product of its digits is 25088, while the sum is 35.

The square root of 78724421 is about 8872.6783442205. The cubic root of 78724421 is about 428.5845308322.

The spelling of 78724421 in words is "seventy-eight million, seven hundred twenty-four thousand, four hundred twenty-one".