77145721 has 2 divisors, whose sum is σ = 77145722. Its totient is φ = 77145720.

The previous prime is 77145709. The next prime is 77145737. The reversal of 77145721 is 12754177.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39200121 + 37945600 = 6261^2 + 6160^2 .

It is an emirp because it is prime and its reverse (12754177) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77145721 - 2¹⁵ = 77112953 is a prime.

It is not a weakly prime, because it can be changed into another prime (77145221) 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, 38572860 + 38572861.

It is an arithmetic number, because the mean of its divisors is an integer number (38572861).

Almost surely, 2^77145721 is an apocalyptic number.

It is an amenable number.

77145721 is a deficient number, since it is larger than the sum of its proper divisors (1).

77145721 is an equidigital number, since it uses as much as digits as its factorization.

77145721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13720, while the sum is 34.

The square root of 77145721 is about 8783.2636872634. The cubic root of 77145721 is about 425.7002913705.

Adding to 77145721 its reverse (12754177), we get a palindrome (89899898).

The spelling of 77145721 in words is "seventy-seven million, one hundred forty-five thousand, seven hundred twenty-one".