66921 has 4 divisors (see below), whose sum is σ = 89232. Its totient is φ = 44612.

The previous prime is 66919. The next prime is 66923. The reversal of 66921 is 12966.

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 an interprime number because it is at equal distance from previous prime (66919) and next prime (66923).

It is a cyclic number.

It is not a de Polignac number, because 66921 - 2¹ = 66919 is a prime.

It is a D-number.

It is a Curzon number.

66921 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 66891 and 66900.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 66921.

It is not an unprimeable number, because it can be changed into a prime (66923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11151 + ... + 11156.

It is an arithmetic number, because the mean of its divisors is an integer number (22308).

2⁶⁶⁹²¹ is an apocalyptic number.

It is an amenable number.

66921 is a deficient number, since it is larger than the sum of its proper divisors (22311).

66921 is a wasteful number, since it uses less digits than its factorization.

66921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22310.

The product of its digits is 648, while the sum is 24.

The square root of 66921 is about 258.6909352877. The cubic root of 66921 is about 40.5995114277.

The spelling of 66921 in words is "sixty-six thousand, nine hundred twenty-one".