866668721 has 8 divisors (see below), whose sum is σ = 920211840. Its totient is φ = 813410368.

The previous prime is 866668657. The next prime is 866668729. The reversal of 866668721 is 127866668.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 866668721 - 2⁶ = 866668657 is a prime.

It is a super-2 number, since 2×866668721² = 1502229343919551682, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 866668721.

It is not an unprimeable number, because it can be changed into a prime (866668729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 64901 + ... + 77106.

It is an arithmetic number, because the mean of its divisors is an integer number (115026480).

Almost surely, 2^866668721 is an apocalyptic number.

It is an amenable number.

866668721 is a deficient number, since it is larger than the sum of its proper divisors (53543119).

866668721 is a wasteful number, since it uses less digits than its factorization.

866668721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142383.

The product of its digits is 1161216, while the sum is 50.

The square root of 866668721 is about 29439.2377788556. The cubic root of 866668721 is about 953.4202553175.

The spelling of 866668721 in words is "eight hundred sixty-six million, six hundred sixty-eight thousand, seven hundred twenty-one".