51565681 has 2 divisors, whose sum is σ = 51565682. Its totient is φ = 51565680.

The previous prime is 51565669. The next prime is 51565697. The reversal of 51565681 is 18656515.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41165056 + 10400625 = 6416^2 + 3225^2 .

It is a cyclic number.

It is not a de Polignac number, because 51565681 - 2⁵ = 51565649 is a prime.

It is a super-2 number, since 2×51565681² = 5318038913987522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 51565681.

It is not a weakly prime, because it can be changed into another prime (51565081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25782840 + 25782841.

It is an arithmetic number, because the mean of its divisors is an integer number (25782841).

Almost surely, 2^51565681 is an apocalyptic number.

It is an amenable number.

51565681 is a deficient number, since it is larger than the sum of its proper divisors (1).

51565681 is an equidigital number, since it uses as much as digits as its factorization.

51565681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36000, while the sum is 37.

The square root of 51565681 is about 7180.9248011659. The cubic root of 51565681 is about 372.2090420455.

The spelling of 51565681 in words is "fifty-one million, five hundred sixty-five thousand, six hundred eighty-one".