666491601 has 8 divisors (see below), whose sum is σ = 919298880. Its totient is φ = 429006032.

The previous prime is 666491597. The next prime is 666491611. The reversal of 666491601 is 106194666.

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 666491601 - 2² = 666491597 is a prime.

It is a super-2 number, since 2×666491601² = 888422108407086402, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 666491601.

It is not an unprimeable number, because it can be changed into a prime (666491611) 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, 3830325 + ... + 3830498.

It is an arithmetic number, because the mean of its divisors is an integer number (114912360).

Almost surely, 2^666491601 is an apocalyptic number.

It is an amenable number.

666491601 is a deficient number, since it is larger than the sum of its proper divisors (252807279).

666491601 is a wasteful number, since it uses less digits than its factorization.

666491601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7660855.

The product of its (nonzero) digits is 46656, while the sum is 39.

The square root of 666491601 is about 25816.4986200685. The cubic root of 666491601 is about 873.5039910687.

The spelling of 666491601 in words is "six hundred sixty-six million, four hundred ninety-one thousand, six hundred one".