3781991 has 4 divisors (see below), whose sum is σ = 3801984. Its totient is φ = 3762000.

The previous prime is 3781961. The next prime is 3781993. The reversal of 3781991 is 1991873.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 3781991 - 2¹⁴ = 3765607 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3781993) 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, 9710 + ... + 10091.

It is an arithmetic number, because the mean of its divisors is an integer number (950496).

Almost surely, 2^3781991 is an apocalyptic number.

3781991 is a deficient number, since it is larger than the sum of its proper divisors (19993).

3781991 is a wasteful number, since it uses less digits than its factorization.

3781991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19992.

The product of its digits is 13608, while the sum is 38.

The square root of 3781991 is about 1944.7341720657. The cubic root of 3781991 is about 155.8021681380.

It can be divided in two parts, 37 and 81991, that added together give a palindrome (82028).

The spelling of 3781991 in words is "three million, seven hundred eighty-one thousand, nine hundred ninety-one".