7661221 has 2 divisors, whose sum is σ = 7661222. Its totient is φ = 7661220.

The previous prime is 7661207. The next prime is 7661233. The reversal of 7661221 is 1221667.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6558721 + 1102500 = 2561^2 + 1050^2 .

It is an emirp because it is prime and its reverse (1221667) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7661221 - 2⁵ = 7661189 is a prime.

It is an Ulam number.

It is equal to p₅₁₈₄₅₂ and since 7661221 and 518452 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7661281) 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 as a sum of consecutive naturals, namely, 3830610 + 3830611.

It is an arithmetic number, because the mean of its divisors is an integer number (3830611).

Almost surely, 2^7661221 is an apocalyptic number.

7661221 is the 1480-th centered heptagonal number.

It is an amenable number.

7661221 is a deficient number, since it is larger than the sum of its proper divisors (1).

7661221 is an equidigital number, since it uses as much as digits as its factorization.

7661221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 25.

The square root of 7661221 is about 2767.8910744464. The cubic root of 7661221 is about 197.1360256832.

Adding to 7661221 its reverse (1221667), we get a palindrome (8882888).

The spelling of 7661221 in words is "seven million, six hundred sixty-one thousand, two hundred twenty-one".