667751221 has 8 divisors (see below), whose sum is σ = 678632984. Its totient is φ = 656916480.

The previous prime is 667751209. The next prime is 667751251. The reversal of 667751221 is 122157766.

It can be written as a sum of positive squares in 4 ways, for example, as 78960996 + 588790225 = 8886^2 + 24265^2 .

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 667751221 - 2⁷ = 667751093 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 (667751251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17461 + ... + 40501.

It is an arithmetic number, because the mean of its divisors is an integer number (84829123).

Almost surely, 2^667751221 is an apocalyptic number.

It is an amenable number.

667751221 is a deficient number, since it is larger than the sum of its proper divisors (10881763).

667751221 is a wasteful number, since it uses less digits than its factorization.

667751221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23511.

The product of its digits is 35280, while the sum is 37.

The square root of 667751221 is about 25840.8827442098. The cubic root of 667751221 is about 874.0539308185.

The spelling of 667751221 in words is "six hundred sixty-seven million, seven hundred fifty-one thousand, two hundred twenty-one".