1917221 has 4 divisors (see below), whose sum is σ = 1920000. Its totient is φ = 1914444.

The previous prime is 1917203. The next prime is 1917239. The reversal of 1917221 is 1227191.

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, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (1917203) and next prime (1917239).

It is a cyclic number.

It is not a de Polignac number, because 1917221 - 2¹⁸ = 1655077 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 (1917281) 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, 530 + ... + 2028.

It is an arithmetic number, because the mean of its divisors is an integer number (480000).

2^1917221 is an apocalyptic number.

It is an amenable number.

1917221 is a deficient number, since it is larger than the sum of its proper divisors (2779).

1917221 is a wasteful number, since it uses less digits than its factorization.

1917221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2778.

The product of its digits is 252, while the sum is 23.

The square root of 1917221 is about 1384.6374976867. The cubic root of 1917221 is about 124.2293060119.

The spelling of 1917221 in words is "one million, nine hundred seventeen thousand, two hundred twenty-one".