66207821 has 2 divisors, whose sum is σ = 66207822. Its totient is φ = 66207820.

The previous prime is 66207811. The next prime is 66207833. The reversal of 66207821 is 12870266.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 58446025 + 7761796 = 7645^2 + 2786^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66207821 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66207811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33103910 + 33103911.

It is an arithmetic number, because the mean of its divisors is an integer number (33103911).

Almost surely, 2^66207821 is an apocalyptic number.

It is an amenable number.

66207821 is a deficient number, since it is larger than the sum of its proper divisors (1).

66207821 is an equidigital number, since it uses as much as digits as its factorization.

66207821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 66207821 is about 8136.8188501404. The cubic root of 66207821 is about 404.5477265920.

It can be divided in two parts, 6620 and 7821, that added together give a palindrome (14441).

The spelling of 66207821 in words is "sixty-six million, two hundred seven thousand, eight hundred twenty-one".