3991551 has 8 divisors (see below), whose sum is σ = 5343360. Its totient is φ = 2650392.

The previous prime is 3991543. The next prime is 3991571. The reversal of 3991551 is 1551993.

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

It is not a de Polignac number, because 3991551 - 2³ = 3991543 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 zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991511) 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, 1741 + ... + 3318.

It is an arithmetic number, because the mean of its divisors is an integer number (667920).

Almost surely, 2^3991551 is an apocalyptic number.

3991551 is a deficient number, since it is larger than the sum of its proper divisors (1351809).

3991551 is a wasteful number, since it uses less digits than its factorization.

3991551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5325.

The product of its digits is 6075, while the sum is 33.

The square root of 3991551 is about 1997.8866334204. The cubic root of 3991551 is about 158.6282601492.

The spelling of 3991551 in words is "three million, nine hundred ninety-one thousand, five hundred fifty-one".