668292821 has 6 divisors (see below), whose sum is σ = 777401910. Its totient is φ = 572822376.

The previous prime is 668292817. The next prime is 668292839. The reversal of 668292821 is 128292866.

It can be written as a sum of positive squares in only one way, i.e., 635745796 + 32547025 = 25214^2 + 5705^2 .

It is not a de Polignac number, because 668292821 - 2² = 668292817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668292841) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6819266 + ... + 6819363.

It is an arithmetic number, because the mean of its divisors is an integer number (129566985).

Almost surely, 2^668292821 is an apocalyptic number.

It is an amenable number.

668292821 is a deficient number, since it is larger than the sum of its proper divisors (109109089).

668292821 is a wasteful number, since it uses less digits than its factorization.

668292821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13638643 (or 13638636 counting only the distinct ones).

The product of its digits is 165888, while the sum is 44.

The square root of 668292821 is about 25851.3601382983. The cubic root of 668292821 is about 874.2901763275.

The spelling of 668292821 in words is "six hundred sixty-eight million, two hundred ninety-two thousand, eight hundred twenty-one".