66021811 has 4 divisors (see below), whose sum is σ = 66038112. Its totient is φ = 66005512.

The previous prime is 66021779. The next prime is 66021853. The reversal of 66021811 is 11812066.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 66021811 - 2⁵ = 66021779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66021871) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3126 + ... + 11908.

It is an arithmetic number, because the mean of its divisors is an integer number (16509528).

Almost surely, 2^66021811 is an apocalyptic number.

66021811 is a deficient number, since it is larger than the sum of its proper divisors (16301).

66021811 is an equidigital number, since it uses as much as digits as its factorization.

66021811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16300.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 66021811 is about 8125.3806680057. The cubic root of 66021811 is about 404.1685140715.

Adding to 66021811 its reverse (11812066), we get a palindrome (77833877).

The spelling of 66021811 in words is "sixty-six million, twenty-one thousand, eight hundred eleven".