667645504365721 has 8 divisors (see below), whose sum is σ = 779257974700800. Its totient is φ = 560091669315648.

The previous prime is 667645504365709. The next prime is 667645504365731. The reversal of 667645504365721 is 127563405546766.

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 667645504365721 - 2²⁵ = 667645470811289 is a prime.

It is not an unprimeable number, because it can be changed into a prime (667645504365731) 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, 1014658820896 + ... + 1014658821553.

It is an arithmetic number, because the mean of its divisors is an integer number (97407246837600).

Almost surely, 2^{667645504365721} is an apocalyptic number.

It is an amenable number.

667645504365721 is a deficient number, since it is larger than the sum of its proper divisors (111612470335079).

667645504365721 is a wasteful number, since it uses less digits than its factorization.

667645504365721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2029317642503.

The product of its (nonzero) digits is 762048000, while the sum is 67.

The spelling of 667645504365721 in words is "six hundred sixty-seven trillion, six hundred forty-five billion, five hundred four million, three hundred sixty-five thousand, seven hundred twenty-one".