1866721 has 2 divisors, whose sum is σ = 1866722. Its totient is φ = 1866720.

The previous prime is 1866679. The next prime is 1866737. The reversal of 1866721 is 1276681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1852321 + 14400 = 1361^2 + 120^2 .

It is a cyclic number.

It is not a de Polignac number, because 1866721 - 2⁷ = 1866593 is a prime.

It is a Chen prime.

It is an Ulam number.

It is equal to p₁₃₉₇₂₉ and since 1866721 and 139729 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (1866751) 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, 933360 + 933361.

It is an arithmetic number, because the mean of its divisors is an integer number (933361).

2^1866721 is an apocalyptic number.

It is an amenable number.

1866721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1866721 is an equidigital number, since it uses as much as digits as its factorization.

1866721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 31.

The square root of 1866721 is about 1366.2799859472. The cubic root of 1866721 is about 123.1288446496.

The spelling of 1866721 in words is "one million, eight hundred sixty-six thousand, seven hundred twenty-one".