681936778 has 4 divisors (see below), whose sum is σ = 1022905170. Its totient is φ = 340968388.

The previous prime is 681936737. The next prime is 681936781. The reversal of 681936778 is 877639186.

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

It can be written as a sum of positive squares in only one way, i.e., 595018449 + 86918329 = 24393^2 + 9323^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 170484193 + ... + 170484196.

Almost surely, 2^681936778 is an apocalyptic number.

681936778 is a deficient number, since it is larger than the sum of its proper divisors (340968392).

681936778 is a wasteful number, since it uses less digits than its factorization.

681936778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 340968391.

The product of its digits is 3048192, while the sum is 55.

The square root of 681936778 is about 26113.9192385976. The cubic root of 681936778 is about 880.2000139365.

The spelling of 681936778 in words is "six hundred eighty-one million, nine hundred thirty-six thousand, seven hundred seventy-eight".