1668520391 has 2 divisors, whose sum is σ = 1668520392. Its totient is φ = 1668520390.

The previous prime is 1668520367. The next prime is 1668520393. The reversal of 1668520391 is 1930258661.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1668520391 - 2¹⁰ = 1668519367 is a prime.

Together with 1668520393, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1668520393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 834260195 + 834260196.

It is an arithmetic number, because the mean of its divisors is an integer number (834260196).

Almost surely, 2^1668520391 is an apocalyptic number.

1668520391 is a deficient number, since it is larger than the sum of its proper divisors (1).

1668520391 is an equidigital number, since it uses as much as digits as its factorization.

1668520391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 77760, while the sum is 41.

The square root of 1668520391 is about 40847.5261307218. The cubic root of 1668520391 is about 1186.0705052749.

The spelling of 1668520391 in words is "one billion, six hundred sixty-eight million, five hundred twenty thousand, three hundred ninety-one".