7278221 has 4 divisors (see below), whose sum is σ = 7309692. Its totient is φ = 7246752.

The previous prime is 7278209. The next prime is 7278239. The reversal of 7278221 is 1228727.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1228727 = 347 ⋅3541.

It can be written as a sum of positive squares in 2 ways, for example, as 4056196 + 3222025 = 2014^2 + 1795^2 .

It is a cyclic number.

It is not a de Polignac number, because 7278221 - 2⁶ = 7278157 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 (7278241) 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, 15386 + ... + 15851.

It is an arithmetic number, because the mean of its divisors is an integer number (1827423).

Almost surely, 2^7278221 is an apocalyptic number.

It is an amenable number.

7278221 is a deficient number, since it is larger than the sum of its proper divisors (31471).

7278221 is a wasteful number, since it uses less digits than its factorization.

7278221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31470.

The product of its digits is 3136, while the sum is 29.

The square root of 7278221 is about 2697.8178218701. The cubic root of 7278221 is about 193.7946333523.

The spelling of 7278221 in words is "seven million, two hundred seventy-eight thousand, two hundred twenty-one".