51695981 has 2 divisors, whose sum is σ = 51695982. Its totient is φ = 51695980.

The previous prime is 51695971. The next prime is 51695983. The reversal of 51695981 is 18959615.

51695981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 47955625 + 3740356 = 6925^2 + 1934^2 .

It is a cyclic number.

It is not a de Polignac number, because 51695981 - 2²² = 47501677 is a prime.

It is a super-2 number, since 2×51695981² = 5344948903104722, which contains 22 as substring.

Together with 51695983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51695983) 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 as a sum of consecutive naturals, namely, 25847990 + 25847991.

It is an arithmetic number, because the mean of its divisors is an integer number (25847991).

Almost surely, 2^51695981 is an apocalyptic number.

It is an amenable number.

51695981 is a deficient number, since it is larger than the sum of its proper divisors (1).

51695981 is an equidigital number, since it uses as much as digits as its factorization.

51695981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 97200, while the sum is 44.

The square root of 51695981 is about 7189.9917246128. The cubic root of 51695981 is about 372.5222868518.

The spelling of 51695981 in words is "fifty-one million, six hundred ninety-five thousand, nine hundred eighty-one".