51688681 has 16 divisors (see below), whose sum is σ = 57492288. Its totient is φ = 46080000.

The previous prime is 51688657. The next prime is 51688697. The reversal of 51688681 is 18688615.

It is a happy number.

51688681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a 5-Lehmer number, since φ(51688681) divides (51688681-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 51688681 - 2⁵ = 51688649 is a prime.

It is a super-2 number, since 2×51688681² = 5343439487039522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (51688601) by changing a digit.

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 in 15 ways as a sum of consecutive naturals, for example, 205806 + ... + 206056.

It is an arithmetic number, because the mean of its divisors is an integer number (3593268).

Almost surely, 2^51688681 is an apocalyptic number.

It is an amenable number.

51688681 is a deficient number, since it is larger than the sum of its proper divisors (5803607).

51688681 is a wasteful number, since it uses less digits than its factorization.

51688681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 552.

The product of its digits is 92160, while the sum is 43.

The square root of 51688681 is about 7189.4840565927. The cubic root of 51688681 is about 372.5047513770.

The spelling of 51688681 in words is "fifty-one million, six hundred eighty-eight thousand, six hundred eighty-one".