1866221 has 4 divisors (see below), whose sum is σ = 2132832. Its totient is φ = 1599612.

The previous prime is 1866211. The next prime is 1866223. The reversal of 1866221 is 1226681.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-1866221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1866223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133295 + ... + 133308.

It is an arithmetic number, because the mean of its divisors is an integer number (533208).

2^1866221 is an apocalyptic number.

It is an amenable number.

1866221 is a deficient number, since it is larger than the sum of its proper divisors (266611).

1866221 is an equidigital number, since it uses as much as digits as its factorization.

1866221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 266610.

The product of its digits is 1152, while the sum is 26.

The square root of 1866221 is about 1366.0969950922. The cubic root of 1866221 is about 123.1178503411.

The spelling of 1866221 in words is "one million, eight hundred sixty-six thousand, two hundred twenty-one".