666712221 has 16 divisors (see below), whose sum is σ = 1016400000. Its totient is φ = 380806848.

The previous prime is 666712219. The next prime is 666712237. The reversal of 666712221 is 122217666.

It is not a de Polignac number, because 666712221 - 2¹ = 666712219 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666712021) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51955 + ... + 63503.

It is an arithmetic number, because the mean of its divisors is an integer number (63525000).

Almost surely, 2^666712221 is an apocalyptic number.

It is an amenable number.

666712221 is a deficient number, since it is larger than the sum of its proper divisors (349687779).

666712221 is a wasteful number, since it uses less digits than its factorization.

666712221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14308.

The product of its digits is 12096, while the sum is 33.

The square root of 666712221 is about 25820.7711155186. The cubic root of 666712221 is about 873.6003619709.

Adding to 666712221 its reverse (122217666), we get a palindrome (788929887).

The spelling of 666712221 in words is "six hundred sixty-six million, seven hundred twelve thousand, two hundred twenty-one".