1668748821 has 4 divisors (see below), whose sum is σ = 2224998432. Its totient is φ = 1112499212.

The previous prime is 1668748819. The next prime is 1668748889. The reversal of 1668748821 is 1288478661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1668748821 - 2¹ = 1668748819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1668748021) 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, 278124801 + ... + 278124806.

It is an arithmetic number, because the mean of its divisors is an integer number (556249608).

Almost surely, 2^1668748821 is an apocalyptic number.

It is an amenable number.

1668748821 is a deficient number, since it is larger than the sum of its proper divisors (556249611).

1668748821 is an equidigital number, since it uses as much as digits as its factorization.

1668748821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 556249610.

The product of its digits is 1032192, while the sum is 51.

The square root of 1668748821 is about 40850.3221651923. The cubic root of 1668748821 is about 1186.1246294206.

The spelling of 1668748821 in words is "one billion, six hundred sixty-eight million, seven hundred forty-eight thousand, eight hundred twenty-one".