77242721 has 2 divisors, whose sum is σ = 77242722. Its totient is φ = 77242720.

The previous prime is 77242703. The next prime is 77242723. The reversal of 77242721 is 12724277.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73342096 + 3900625 = 8564^2 + 1975^2 .

It is an emirp because it is prime and its reverse (12724277) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77242721 - 2¹⁴ = 77226337 is a prime.

Together with 77242723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (77242723) 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, 38621360 + 38621361.

It is an arithmetic number, because the mean of its divisors is an integer number (38621361).

Almost surely, 2^77242721 is an apocalyptic number.

It is an amenable number.

77242721 is a deficient number, since it is larger than the sum of its proper divisors (1).

77242721 is an equidigital number, since it uses as much as digits as its factorization.

77242721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10976, while the sum is 32.

The square root of 77242721 is about 8788.7838180262. The cubic root of 77242721 is about 425.8786362530.

Adding to 77242721 its reverse (12724277), we get a palindrome (89966998).

The spelling of 77242721 in words is "seventy-seven million, two hundred forty-two thousand, seven hundred twenty-one".