66858821 has 4 divisors (see below), whose sum is σ = 67022700. Its totient is φ = 66694944.

The previous prime is 66858817. The next prime is 66858839. The reversal of 66858821 is 12885866.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 47761921 + 19096900 = 6911^2 + 4370^2 .

It is a cyclic number.

It is not a de Polignac number, because 66858821 - 2² = 66858817 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 (66858871) 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, 81326 + ... + 82143.

It is an arithmetic number, because the mean of its divisors is an integer number (16755675).

Almost surely, 2^66858821 is an apocalyptic number.

It is an amenable number.

66858821 is a deficient number, since it is larger than the sum of its proper divisors (163879).

66858821 is a wasteful number, since it uses less digits than its factorization.

66858821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163878.

The product of its digits is 184320, while the sum is 44.

The square root of 66858821 is about 8176.7243441368. The cubic root of 66858821 is about 405.8693331682.

The spelling of 66858821 in words is "sixty-six million, eight hundred fifty-eight thousand, eight hundred twenty-one".