3991081 has 4 divisors (see below), whose sum is σ = 4017664. Its totient is φ = 3964500.

The previous prime is 3991051. The next prime is 3991087. The reversal of 3991081 is 1801993.

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 an emirpimes, since its reverse is a distinct semiprime: 1801993 = 179 ⋅10067.

It is a cyclic number.

It is not a de Polignac number, because 3991081 - 2¹⁵ = 3958313 is a prime.

It is a super-2 number, since 2×3991081² = 31857455097122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3991087) 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, 13065 + ... + 13366.

It is an arithmetic number, because the mean of its divisors is an integer number (1004416).

Almost surely, 2^3991081 is an apocalyptic number.

3991081 is the 1264-th centered pentagonal number.

It is an amenable number.

3991081 is a deficient number, since it is larger than the sum of its proper divisors (26583).

3991081 is a wasteful number, since it uses less digits than its factorization.

3991081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26582.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 3991081 is about 1997.7690056661. The cubic root of 3991081 is about 158.6220338135.

The spelling of 3991081 in words is "three million, nine hundred ninety-one thousand, eighty-one".