77772221 has 2 divisors, whose sum is σ = 77772222. Its totient is φ = 77772220.

The previous prime is 77772209. The next prime is 77772241. The reversal of 77772221 is 12227777.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75446596 + 2325625 = 8686^2 + 1525^2 .

It is a cyclic number.

It is not a de Polignac number, because 77772221 - 2⁶ = 77772157 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 (77772241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38886110 + 38886111.

It is an arithmetic number, because the mean of its divisors is an integer number (38886111).

Almost surely, 2^77772221 is an apocalyptic number.

It is an amenable number.

77772221 is a deficient number, since it is larger than the sum of its proper divisors (1).

77772221 is an equidigital number, since it uses as much as digits as its factorization.

77772221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19208, while the sum is 35.

The square root of 77772221 is about 8818.8559915672. The cubic root of 77772221 is about 426.8495558578.

Adding to 77772221 its reverse (12227777), we get a palindrome (89999998).

The spelling of 77772221 in words is "seventy-seven million, seven hundred seventy-two thousand, two hundred twenty-one".