681813949 has 4 divisors (see below), whose sum is σ = 681947964. Its totient is φ = 681679936.

The previous prime is 681813931. The next prime is 681813953. The reversal of 681813949 is 949318186.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 949318186 = 2 ⋅474659093.

It can be written as a sum of positive squares in 2 ways, for example, as 467337924 + 214476025 = 21618^2 + 14645^2 .

It is a cyclic number.

It is not a de Polignac number, because 681813949 - 2¹⁵ = 681781181 is a prime.

It is a super-2 number, since 2×681813949² = 929740522101949202, which contains 22 as substring.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681813749) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 59062 + ... + 69655.

It is an arithmetic number, because the mean of its divisors is an integer number (170486991).

Almost surely, 2^681813949 is an apocalyptic number.

It is an amenable number.

681813949 is a deficient number, since it is larger than the sum of its proper divisors (134015).

681813949 is a wasteful number, since it uses less digits than its factorization.

681813949 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134014.

The product of its digits is 373248, while the sum is 49.

The square root of 681813949 is about 26111.5673409315. The cubic root of 681813949 is about 880.1471641794.

The spelling of 681813949 in words is "six hundred eighty-one million, eight hundred thirteen thousand, nine hundred forty-nine".