66320821 has 16 divisors (see below), whose sum is σ = 78825600. Its totient is φ = 54616320.

The previous prime is 66320809. The next prime is 66320833. The reversal of 66320821 is 12802366.

It is an interprime number because it is at equal distance from previous prime (66320809) and next prime (66320833).

It is a cyclic number.

It is not a de Polignac number, because 66320821 - 2⁵ = 66320789 is a prime.

It is a super-2 number, since 2×66320821² = 8796902596228082, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 66320821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66320321) 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 15 ways as a sum of consecutive naturals, for example, 17505 + ... + 20953.

It is an arithmetic number, because the mean of its divisors is an integer number (4926600).

Almost surely, 2^66320821 is an apocalyptic number.

It is an amenable number.

66320821 is a deficient number, since it is larger than the sum of its proper divisors (12504779).

66320821 is a wasteful number, since it uses less digits than its factorization.

66320821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3564.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 66320821 is about 8143.7596354509. The cubic root of 66320821 is about 404.7777493179. Note that the first 4 decimals are identical.

The spelling of 66320821 in words is "sixty-six million, three hundred twenty thousand, eight hundred twenty-one".