77643221 has 2 divisors, whose sum is σ = 77643222. Its totient is φ = 77643220.

The previous prime is 77643187. The next prime is 77643227. The reversal of 77643221 is 12234677.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66178225 + 11464996 = 8135^2 + 3386^2 .

It is a cyclic number.

It is not a de Polignac number, because 77643221 - 2⁶ = 77643157 is a prime.

It is a Chen prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77643227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38821610 + 38821611.

It is an arithmetic number, because the mean of its divisors is an integer number (38821611).

Almost surely, 2^77643221 is an apocalyptic number.

It is an amenable number.

77643221 is a deficient number, since it is larger than the sum of its proper divisors (1).

77643221 is an equidigital number, since it uses as much as digits as its factorization.

77643221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14112, while the sum is 32.

The square root of 77643221 is about 8811.5390823624. The cubic root of 77643221 is about 426.6134215647.

Adding to 77643221 its reverse (12234677), we get a palindrome (89877898).

The spelling of 77643221 in words is "seventy-seven million, six hundred forty-three thousand, two hundred twenty-one".