1991217 has 8 divisors (see below), whose sum is σ = 2663424. Its totient is φ = 1323248.

The previous prime is 1991189. The next prime is 1991239. The reversal of 1991217 is 7121991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1991217 - 2⁶ = 1991153 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991267) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 283 + ... + 2015.

It is an arithmetic number, because the mean of its divisors is an integer number (332928).

2^1991217 is an apocalyptic number.

It is an amenable number.

1991217 is a deficient number, since it is larger than the sum of its proper divisors (672207).

1991217 is a wasteful number, since it uses less digits than its factorization.

1991217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2119.

The product of its digits is 1134, while the sum is 30.

The square root of 1991217 is about 1411.1048862505. The cubic root of 1991217 is about 125.8074029090.

The spelling of 1991217 in words is "one million, nine hundred ninety-one thousand, two hundred seventeen".