78284021 has 18 divisors (see below), whose sum is σ = 85288770. Its totient is φ = 71766240.

The previous prime is 78283993. The next prime is 78284053. The reversal of 78284021 is 12048287.

It can be written as a sum of positive squares in 3 ways, for example, as 27447121 + 50836900 = 5239^2 + 7130^2 .

It is a de Polignac number, because none of the positive numbers 2^k-78284021 is a prime.

It is a super-2 number, since 2×78284021² = 12256775887856882, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78284221) 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 17 ways as a sum of consecutive naturals, for example, 1477031 + ... + 1477083.

It is an arithmetic number, because the mean of its divisors is an integer number (4738265).

Almost surely, 2^78284021 is an apocalyptic number.

It is an amenable number.

78284021 is a deficient number, since it is larger than the sum of its proper divisors (7004749).

78284021 is an equidigital number, since it uses as much as digits as its factorization.

78284021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197 (or 113 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 32.

The square root of 78284021 is about 8847.8257781220. The cubic root of 78284021 is about 427.7838403194.

The spelling of 78284021 in words is "seventy-eight million, two hundred eighty-four thousand, twenty-one".