77556421 has 2 divisors, whose sum is σ = 77556422. Its totient is φ = 77556420.

The previous prime is 77556371. The next prime is 77556449. The reversal of 77556421 is 12465577.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74632321 + 2924100 = 8639^2 + 1710^2 .

It is a cyclic number.

It is not a de Polignac number, because 77556421 - 2⁹ = 77555909 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77556491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38778210 + 38778211.

It is an arithmetic number, because the mean of its divisors is an integer number (38778211).

Almost surely, 2^77556421 is an apocalyptic number.

77556421 is the 5085-th hex number.

It is an amenable number.

77556421 is a deficient number, since it is larger than the sum of its proper divisors (1).

77556421 is an equidigital number, since it uses as much as digits as its factorization.

77556421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 58800, while the sum is 37.

The square root of 77556421 is about 8806.6123452778. The cubic root of 77556421 is about 426.4543870642.

It can be divided in two parts, 77556 and 421, that added together give a palindrome (77977).

The spelling of 77556421 in words is "seventy-seven million, five hundred fifty-six thousand, four hundred twenty-one".