66650021 has 4 divisors (see below), whose sum is σ = 69547872. Its totient is φ = 63752172.

The previous prime is 66649993. The next prime is 66650027. The reversal of 66650021 is 12005666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66650021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66650027) 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 in 3 ways as a sum of consecutive naturals, for example, 1448891 + ... + 1448936.

It is an arithmetic number, because the mean of its divisors is an integer number (17386968).

Almost surely, 2^66650021 is an apocalyptic number.

It is an amenable number.

66650021 is a deficient number, since it is larger than the sum of its proper divisors (2897851).

66650021 is a wasteful number, since it uses less digits than its factorization.

66650021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2897850.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 66650021 is about 8163.9464108971. The cubic root of 66650021 is about 405.4463827934.

Adding to 66650021 its reverse (12005666), we get a palindrome (78655687).

The spelling of 66650021 in words is "sixty-six million, six hundred fifty thousand, twenty-one".