1807921 has 2 divisors, whose sum is σ = 1807922. Its totient is φ = 1807920.

The previous prime is 1807913. The next prime is 1807943. The reversal of 1807921 is 1297081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1795600 + 12321 = 1340^2 + 111^2 .

It is a cyclic number.

It is not a de Polignac number, because 1807921 - 2³ = 1807913 is a prime.

1807921 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1807921.

It is not a weakly prime, because it can be changed into another prime (1807121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 903960 + 903961.

It is an arithmetic number, because the mean of its divisors is an integer number (903961).

2^1807921 is an apocalyptic number.

It is an amenable number.

1807921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1807921 is an equidigital number, since it uses as much as digits as its factorization.

1807921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 1807921 is about 1344.5895284435. The cubic root of 1807921 is about 121.8222125988.

The spelling of 1807921 in words is "one million, eight hundred seven thousand, nine hundred twenty-one".