1668521 has 2 divisors, whose sum is σ = 1668522. Its totient is φ = 1668520.

The previous prime is 1668517. The next prime is 1668539. The reversal of 1668521 is 1258661.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1590121 + 78400 = 1261^2 + 280^2 .

It is an emirp because it is prime and its reverse (1258661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1668521 - 2² = 1668517 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1668551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 834260 + 834261.

It is an arithmetic number, because the mean of its divisors is an integer number (834261).

2^1668521 is an apocalyptic number.

It is an amenable number.

1668521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1668521 is an equidigital number, since it uses as much as digits as its factorization.

1668521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 29.

The square root of 1668521 is about 1291.7124292969. The cubic root of 1668521 is about 118.6070649578.

The spelling of 1668521 in words is "one million, six hundred sixty-eight thousand, five hundred twenty-one".