8491781 has 4 divisors (see below), whose sum is σ = 8618592. Its totient is φ = 8364972.

The previous prime is 8491753. The next prime is 8491801. The reversal of 8491781 is 1871948.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8491781 is a prime.

It is a super-2 number, since 2×8491781² = 144220689103922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8491711) 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, 63305 + ... + 63438.

It is an arithmetic number, because the mean of its divisors is an integer number (2154648).

Almost surely, 2^8491781 is an apocalyptic number.

It is an amenable number.

8491781 is a deficient number, since it is larger than the sum of its proper divisors (126811).

8491781 is a wasteful number, since it uses less digits than its factorization.

8491781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126810.

The product of its digits is 16128, while the sum is 38.

The square root of 8491781 is about 2914.0660596493. The cubic root of 8491781 is about 204.0169552100.

The spelling of 8491781 in words is "eight million, four hundred ninety-one thousand, seven hundred eighty-one".