66567821 has 2 divisors, whose sum is σ = 66567822. Its totient is φ = 66567820.

The previous prime is 66567799. The next prime is 66567829. The reversal of 66567821 is 12876566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 50965321 + 15602500 = 7139^2 + 3950^2 .

It is a cyclic number.

It is not a de Polignac number, because 66567821 - 2¹⁴ = 66551437 is a prime.

It is equal to p_3927785 and since 66567821 and 3927785 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66567829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33283910 + 33283911.

It is an arithmetic number, because the mean of its divisors is an integer number (33283911).

Almost surely, 2^66567821 is an apocalyptic number.

It is an amenable number.

66567821 is a deficient number, since it is larger than the sum of its proper divisors (1).

66567821 is an equidigital number, since it uses as much as digits as its factorization.

66567821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 120960, while the sum is 41.

The square root of 66567821 is about 8158.9105277604. The cubic root of 66567821 is about 405.2796341430.

It can be divided in two parts, 665 and 67821, that added together give a palindrome (68486).

The spelling of 66567821 in words is "sixty-six million, five hundred sixty-seven thousand, eight hundred twenty-one".