1668311621 has 2 divisors, whose sum is σ = 1668311622. Its totient is φ = 1668311620.

The previous prime is 1668311573. The next prime is 1668311629. The reversal of 1668311621 is 1261138661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1227731521 + 440580100 = 35039^2 + 20990^2 .

It is a cyclic number.

It is not a de Polignac number, because 1668311621 - 2¹⁰ = 1668310597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1668311629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 834155810 + 834155811.

It is an arithmetic number, because the mean of its divisors is an integer number (834155811).

Almost surely, 2^1668311621 is an apocalyptic number.

It is an amenable number.

1668311621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1668311621 is an equidigital number, since it uses as much as digits as its factorization.

1668311621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 35.

The square root of 1668311621 is about 40844.9705716628. The cubic root of 1668311621 is about 1186.0210350439.

The spelling of 1668311621 in words is "one billion, six hundred sixty-eight million, three hundred eleven thousand, six hundred twenty-one".