1813681 has 2 divisors, whose sum is σ = 1813682. Its totient is φ = 1813680.

The previous prime is 1813673. The next prime is 1813699. The reversal of 1813681 is 1863181.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1199025 + 614656 = 1095^2 + 784^2 .

It is an emirp because it is prime and its reverse (1863181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1813681 - 2³ = 1813673 is a prime.

It is a super-2 number, since 2×1813681² = 6578877539522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1813081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 906840 + 906841.

It is an arithmetic number, because the mean of its divisors is an integer number (906841).

2^1813681 is an apocalyptic number.

It is an amenable number.

1813681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1813681 is an equidigital number, since it uses as much as digits as its factorization.

1813681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 28.

The square root of 1813681 is about 1346.7297427472. The cubic root of 1813681 is about 121.9514498210.

The spelling of 1813681 in words is "one million, eight hundred thirteen thousand, six hundred eighty-one".