51247781 has 4 divisors (see below), whose sum is σ = 55189932. Its totient is φ = 47305632.

The previous prime is 51247759. The next prime is 51247789. The reversal of 51247781 is 18774215.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18774215 = 5 ⋅3754843.

It can be written as a sum of positive squares in 2 ways, for example, as 11115556 + 40132225 = 3334^2 + 6335^2 .

It is a cyclic number.

It is not a de Polignac number, because 51247781 - 2⁶ = 51247717 is a prime.

It is a super-2 number, since 2×51247781² = 5252670114847922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51247789) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1971056 + ... + 1971081.

It is an arithmetic number, because the mean of its divisors is an integer number (13797483).

Almost surely, 2^51247781 is an apocalyptic number.

It is an amenable number.

51247781 is a deficient number, since it is larger than the sum of its proper divisors (3942151).

51247781 is a wasteful number, since it uses less digits than its factorization.

51247781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3942150.

The product of its digits is 15680, while the sum is 35.

The square root of 51247781 is about 7158.7555482779. The cubic root of 51247781 is about 371.4425810650.

The spelling of 51247781 in words is "fifty-one million, two hundred forty-seven thousand, seven hundred eighty-one".