3991381 has 8 divisors (see below), whose sum is σ = 4109184. Its totient is φ = 3875040.

The previous prime is 3991369. The next prime is 3991399. The reversal of 3991381 is 1831993.

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 3991381 - 2¹¹ = 3989333 is a prime.

It is a super-2 number, since 2×3991381² = 31862244574322, which contains 22 as substring.

It is a Duffinian number.

3991381 is a lucky number.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991321) 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, 7401 + ... + 7921.

It is an arithmetic number, because the mean of its divisors is an integer number (513648).

Almost surely, 2^3991381 is an apocalyptic number.

It is an amenable number.

3991381 is a deficient number, since it is larger than the sum of its proper divisors (117803).

3991381 is a wasteful number, since it uses less digits than its factorization.

3991381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 731.

The product of its digits is 5832, while the sum is 34.

The square root of 3991381 is about 1997.8440880109. The cubic root of 3991381 is about 158.6260081268.

The spelling of 3991381 in words is "three million, nine hundred ninety-one thousand, three hundred eighty-one".