68537781 has 18 divisors (see below), whose sum is σ = 107202498. Its totient is φ = 42176160.

The previous prime is 68537771. The next prime is 68537803. The reversal of 68537781 is 18773586.

It can be written as a sum of positive squares in 3 ways, for example, as 4137156 + 64400625 = 2034^2 + 8025^2 .

It is a de Polignac number, because none of the positive numbers 2^k-68537781 is a prime.

It is a super-2 number, since 2×68537781² = 9394854848807922, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (68537741) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 21010 + ... + 24051.

Almost surely, 2^68537781 is an apocalyptic number.

It is an amenable number.

68537781 is a deficient number, since it is larger than the sum of its proper divisors (38664717).

68537781 is a wasteful number, since it uses less digits than its factorization.

68537781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45093 (or 45077 counting only the distinct ones).

The product of its digits is 282240, while the sum is 45.

The square root of 68537781 is about 8278.7547976734. The cubic root of 68537781 is about 409.2386843772.

The spelling of 68537781 in words is "sixty-eight million, five hundred thirty-seven thousand, seven hundred eighty-one".