641666 has 4 divisors (see below), whose sum is σ = 962502. Its totient is φ = 320832.

The previous prime is 641639. The next prime is 641681. The reversal of 641666 is 666146.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 461041 + 180625 = 679^2 + 425^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160415 + ... + 160418.

2⁶⁴¹⁶⁶⁶ is an apocalyptic number.

641666 is a deficient number, since it is larger than the sum of its proper divisors (320836).

641666 is a wasteful number, since it uses less digits than its factorization.

641666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320835.

The product of its digits is 5184, while the sum is 29.

The square root of 641666 is about 801.0405732546. The cubic root of 641666 is about 86.2520996478.

The spelling of 641666 in words is "six hundred forty-one thousand, six hundred sixty-six".