1661851 has 2 divisors, whose sum is σ = 1661852. Its totient is φ = 1661850.

The previous prime is 1661839. The next prime is 1661857. The reversal of 1661851 is 1581661.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1661851 - 2¹⁵ = 1629083 is a prime.

1661851 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (1661857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830925 + 830926.

It is an arithmetic number, because the mean of its divisors is an integer number (830926).

2^1661851 is an apocalyptic number.

1661851 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661851 is an equidigital number, since it uses as much as digits as its factorization.

1661851 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 28.

The square root of 1661851 is about 1289.1279998511. The cubic root of 1661851 is about 118.4488079071.

The spelling of 1661851 in words is "one million, six hundred sixty-one thousand, eight hundred fifty-one".