78224021 has 16 divisors (see below), whose sum is σ = 84802608. Its totient is φ = 71884800.

The previous prime is 78224017. The next prime is 78224039. The reversal of 78224021 is 12042287.

It can be written as a sum of positive squares in 8 ways, for example, as 10491121 + 67732900 = 3239^2 + 8230^2 .

It is a cyclic number.

It is not a de Polignac number, because 78224021 - 2² = 78224017 is a prime.

It is a super-2 number, since 2×78224021² = 12237994922816882, 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 (78224221) 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 15 ways as a sum of consecutive naturals, for example, 249761 + ... + 250073.

It is an arithmetic number, because the mean of its divisors is an integer number (5300163).

Almost surely, 2^78224021 is an apocalyptic number.

It is an amenable number.

78224021 is a deficient number, since it is larger than the sum of its proper divisors (6578587).

78224021 is a wasteful number, since it uses less digits than its factorization.

78224021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 632.

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 78224021 is about 8844.4344646789. The cubic root of 78224021 is about 427.6745221797.

The spelling of 78224021 in words is "seventy-eight million, two hundred twenty-four thousand, twenty-one".