1668640801 has 3 divisors (see below), whose sum is σ = 1668681651. Its totient is φ = 1668599952.

The previous prime is 1668640783. The next prime is 1668640807. The reversal of 1668640801 is 1080468661.

The square root of 1668640801 is 40849.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 1132255201 + 536385600 = 33649^2 + 23160^2 .

It is not a de Polignac number, because 1668640801 - 2⁵ = 1668640769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1668640807) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 20425 + ... + 61273.

It is an arithmetic number, because the mean of its divisors is an integer number (556227217).

Almost surely, 2^1668640801 is an apocalyptic number.

1668640801 is the 40849-th square number.

1668640801 is the 20425-th centered octagonal number.

It is an amenable number.

1668640801 is a deficient number, since it is larger than the sum of its proper divisors (40850).

1668640801 is an frugal number, since it uses more digits than its factorization.

1668640801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81698 (or 40849 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 40.

The cubic root of 1668640801 is about 1186.0990358051.

The spelling of 1668640801 in words is "one billion, six hundred sixty-eight million, six hundred forty thousand, eight hundred one".