1991247 has 8 divisors (see below), whose sum is σ = 2719920. Its totient is φ = 1295040.

The previous prime is 1991243. The next prime is 1991251. The reversal of 1991247 is 7421991.

It is an interprime number because it is at equal distance from previous prime (1991243) and next prime (1991251).

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

It is not a de Polignac number, because 1991247 - 2² = 1991243 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991243) 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, 7972 + ... + 8217.

It is an arithmetic number, because the mean of its divisors is an integer number (339990).

2^1991247 is an apocalyptic number.

1991247 is a deficient number, since it is larger than the sum of its proper divisors (728673).

1991247 is a wasteful number, since it uses less digits than its factorization.

1991247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16233.

The product of its digits is 4536, while the sum is 33.

The square root of 1991247 is about 1411.1155161786. The cubic root of 1991247 is about 125.8080347174.

The spelling of 1991247 in words is "one million, nine hundred ninety-one thousand, two hundred forty-seven".