7978221 has 6 divisors (see below), whose sum is σ = 11524110. Its totient is φ = 5318808.

The previous prime is 7978211. The next prime is 7978237. The reversal of 7978221 is 1228797.

It can be written as a sum of positive squares in only one way, i.e., 7502121 + 476100 = 2739^2 + 690^2 .

It is not a de Polignac number, because 7978221 - 2⁵ = 7978189 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7978211) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 443226 + ... + 443243.

It is an arithmetic number, because the mean of its divisors is an integer number (1920685).

Almost surely, 2^7978221 is an apocalyptic number.

It is an amenable number.

7978221 is a deficient number, since it is larger than the sum of its proper divisors (3545889).

7978221 is a wasteful number, since it uses less digits than its factorization.

7978221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 886475 (or 886472 counting only the distinct ones).

The product of its digits is 14112, while the sum is 36.

The square root of 7978221 is about 2824.5744812272. The cubic root of 7978221 is about 199.8183433877.

The spelling of 7978221 in words is "seven million, nine hundred seventy-eight thousand, two hundred twenty-one".