77777221 has 2 divisors, whose sum is σ = 77777222. Its totient is φ = 77777220.

The previous prime is 77777197. The next prime is 77777251. The reversal of 77777221 is 12277777.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 51624225 + 26152996 = 7185^2 + 5114^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77777221 is a prime.

It is a super-2 number, since 2×77777221² = 12098592212965682, which contains 22 as substring.

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 (77777251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38888610 + 38888611.

It is an arithmetic number, because the mean of its divisors is an integer number (38888611).

Almost surely, 2^77777221 is an apocalyptic number.

It is an amenable number.

77777221 is a deficient number, since it is larger than the sum of its proper divisors (1).

77777221 is an equidigital number, since it uses as much as digits as its factorization.

77777221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 67228, while the sum is 40.

The square root of 77777221 is about 8819.1394704926. The cubic root of 77777221 is about 426.8587030915.

The spelling of 77777221 in words is "seventy-seven million, seven hundred seventy-seven thousand, two hundred twenty-one".