7881221 has 2 divisors, whose sum is σ = 7881222. Its totient is φ = 7881220.

The previous prime is 7881193. The next prime is 7881227. The reversal of 7881221 is 1221887.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6558721 + 1322500 = 2561^2 + 1150^2 .

It is a cyclic number.

It is not a de Polignac number, because 7881221 - 2¹⁴ = 7864837 is a prime.

It is a super-2 number, since 2×7881221² = 124227288901682, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7881227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3940610 + 3940611.

It is an arithmetic number, because the mean of its divisors is an integer number (3940611).

Almost surely, 2^7881221 is an apocalyptic number.

It is an amenable number.

7881221 is a deficient number, since it is larger than the sum of its proper divisors (1).

7881221 is an equidigital number, since it uses as much as digits as its factorization.

7881221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1792, while the sum is 29.

The square root of 7881221 is about 2807.3512427197. The cubic root of 7881221 is about 199.0052354203.

The spelling of 7881221 in words is "seven million, eight hundred eighty-one thousand, two hundred twenty-one".