51388781 has 2 divisors, whose sum is σ = 51388782. Its totient is φ = 51388780.

The previous prime is 51388751. The next prime is 51388817. The reversal of 51388781 is 18788315.

Together with next prime (51388817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39375625 + 12013156 = 6275^2 + 3466^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51388781 is a prime.

It is a super-2 number, since 2×51388781² = 5281613625331922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51388721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25694390 + 25694391.

It is an arithmetic number, because the mean of its divisors is an integer number (25694391).

Almost surely, 2^51388781 is an apocalyptic number.

It is an amenable number.

51388781 is a deficient number, since it is larger than the sum of its proper divisors (1).

51388781 is an equidigital number, since it uses as much as digits as its factorization.

51388781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 53760, while the sum is 41.

The square root of 51388781 is about 7168.5968641011. The cubic root of 51388781 is about 371.7829238978.

The spelling of 51388781 in words is "fifty-one million, three hundred eighty-eight thousand, seven hundred eighty-one".