66006621 has 6 divisors (see below), whose sum is σ = 95342910. Its totient is φ = 44004408.

The previous prime is 66006617. The next prime is 66006643. The reversal of 66006621 is 12660066.

It can be written as a sum of positive squares in only one way, i.e., 65124900 + 881721 = 8070^2 + 939^2 .

It is not a de Polignac number, because 66006621 - 2² = 66006617 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66006601) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3667026 + ... + 3667043.

It is an arithmetic number, because the mean of its divisors is an integer number (15890485).

Almost surely, 2^66006621 is an apocalyptic number.

It is an amenable number.

66006621 is a deficient number, since it is larger than the sum of its proper divisors (29336289).

66006621 is a wasteful number, since it uses less digits than its factorization.

66006621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7334075 (or 7334072 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 66006621 is about 8124.4458887976. The cubic root of 66006621 is about 404.1375152721.

Adding to 66006621 its reverse (12660066), we get a palindrome (78666687).

The spelling of 66006621 in words is "sixty-six million, six thousand, six hundred twenty-one".