666620671 has 4 divisors (see below), whose sum is σ = 666793512. Its totient is φ = 666447832.

The previous prime is 666620657. The next prime is 666620687. The reversal of 666620671 is 176026666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 176026666 = 2 ⋅88013333.

It is a cyclic number.

It is not a de Polignac number, because 666620671 - 2⁵ = 666620639 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 (666620771) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 80500 + ... + 88393.

It is an arithmetic number, because the mean of its divisors is an integer number (166698378).

Almost surely, 2^666620671 is an apocalyptic number.

666620671 is a deficient number, since it is larger than the sum of its proper divisors (172841).

666620671 is a wasteful number, since it uses less digits than its factorization.

666620671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172840.

The product of its (nonzero) digits is 108864, while the sum is 40.

The square root of 666620671 is about 25818.9982570974. The cubic root of 666620671 is about 873.5603738163.

The spelling of 666620671 in words is "six hundred sixty-six million, six hundred twenty thousand, six hundred seventy-one".