51516781 has 2 divisors, whose sum is σ = 51516782. Its totient is φ = 51516780.

The previous prime is 51516739. The next prime is 51516793. The reversal of 51516781 is 18761515.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 29106025 + 22410756 = 5395^2 + 4734^2 .

It is a cyclic number.

It is not a de Polignac number, because 51516781 - 2²⁵ = 17962349 is a prime.

It is a super-2 number, since 2×51516781² = 5307957449203922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51516701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25758390 + 25758391.

It is an arithmetic number, because the mean of its divisors is an integer number (25758391).

Almost surely, 2^51516781 is an apocalyptic number.

It is an amenable number.

51516781 is a deficient number, since it is larger than the sum of its proper divisors (1).

51516781 is an equidigital number, since it uses as much as digits as its factorization.

51516781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8400, while the sum is 34.

The square root of 51516781 is about 7177.5191396471. The cubic root of 51516781 is about 372.0913489195.

The spelling of 51516781 in words is "fifty-one million, five hundred sixteen thousand, seven hundred eighty-one".