1668561 has 16 divisors (see below), whose sum is σ = 2379840. Its totient is φ = 1036800.

The previous prime is 1668553. The next prime is 1668587. The reversal of 1668561 is 1658661.

It is not a de Polignac number, because 1668561 - 2³ = 1668553 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1668521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3961 + ... + 4361.

It is an arithmetic number, because the mean of its divisors is an integer number (148740).

2^1668561 is an apocalyptic number.

It is an amenable number.

1668561 is a deficient number, since it is larger than the sum of its proper divisors (711279).

1668561 is a wasteful number, since it uses less digits than its factorization.

1668561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 496.

The product of its digits is 8640, while the sum is 33.

The square root of 1668561 is about 1291.7279125265. The cubic root of 1668561 is about 118.6080127522.

The spelling of 1668561 in words is "one million, six hundred sixty-eight thousand, five hundred sixty-one".