77081821 has 2 divisors, whose sum is σ = 77081822. Its totient is φ = 77081820.

The previous prime is 77081813. The next prime is 77081827. The reversal of 77081821 is 12818077.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 76912900 + 168921 = 8770^2 + 411^2 .

It is a cyclic number.

It is not a de Polignac number, because 77081821 - 2³ = 77081813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77081827) 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, 38540910 + 38540911.

It is an arithmetic number, because the mean of its divisors is an integer number (38540911).

Almost surely, 2^77081821 is an apocalyptic number.

It is an amenable number.

77081821 is a deficient number, since it is larger than the sum of its proper divisors (1).

77081821 is an equidigital number, since it uses as much as digits as its factorization.

77081821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6272, while the sum is 34.

The square root of 77081821 is about 8779.6253336916. The cubic root of 77081821 is about 425.5827226866.

Adding to 77081821 its reverse (12818077), we get a palindrome (89899898).

The spelling of 77081821 in words is "seventy-seven million, eighty-one thousand, eight hundred twenty-one".