3181781 has 2 divisors, whose sum is σ = 3181782. Its totient is φ = 3181780.

The previous prime is 3181777. The next prime is 3181813. The reversal of 3181781 is 1871813.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2588881 + 592900 = 1609^2 + 770^2 .

It is an emirp because it is prime and its reverse (1871813) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 3181781 - 2² = 3181777 is a prime.

It is a super-2 number, since 2×3181781² = 20247460663922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3181081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1590890 + 1590891.

It is an arithmetic number, because the mean of its divisors is an integer number (1590891).

Almost surely, 2^3181781 is an apocalyptic number.

It is an amenable number.

3181781 is a deficient number, since it is larger than the sum of its proper divisors (1).

3181781 is an equidigital number, since it uses as much as digits as its factorization.

3181781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1344, while the sum is 29.

The square root of 3181781 is about 1783.7547477162. The cubic root of 3181781 is about 147.0810634694.

The spelling of 3181781 in words is "three million, one hundred eighty-one thousand, seven hundred eighty-one".