78451821 has 48 divisors (see below), whose sum is σ = 142257024. Its totient is φ = 42177024.

The previous prime is 78451811. The next prime is 78451831. The reversal of 78451821 is 12815487.

It is an interprime number because it is at equal distance from previous prime (78451811) and next prime (78451831).

It is not a de Polignac number, because 78451821 - 2⁹ = 78451309 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78451811) 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 47 ways as a sum of consecutive naturals, for example, 27561 + ... + 30273.

It is an arithmetic number, because the mean of its divisors is an integer number (2963688).

Almost surely, 2^78451821 is an apocalyptic number.

It is an amenable number.

78451821 is a deficient number, since it is larger than the sum of its proper divisors (63805203).

78451821 is a wasteful number, since it uses less digits than its factorization.

78451821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2752 (or 2740 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 78451821 is about 8857.3032577642. The cubic root of 78451821 is about 428.0892704727.

The spelling of 78451821 in words is "seventy-eight million, four hundred fifty-one thousand, eight hundred twenty-one".