51378781 has 8 divisors (see below), whose sum is σ = 52731000. Its totient is φ = 50031360.

The previous prime is 51378779. The next prime is 51378799. The reversal of 51378781 is 18787315.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 3006756 + 48372025 = 1734^2 + 6955^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 51378781 - 2¹ = 51378779 is a prime.

It is a super-2 number, since 2×51378781² = 5279558274091922, 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 (51378181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32395 + ... + 33943.

It is an arithmetic number, because the mean of its divisors is an integer number (6591375).

Almost surely, 2^51378781 is an apocalyptic number.

It is an amenable number.

51378781 is a deficient number, since it is larger than the sum of its proper divisors (1352219).

51378781 is a wasteful number, since it uses less digits than its factorization.

51378781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2399.

The product of its digits is 47040, while the sum is 40.

The square root of 51378781 is about 7167.8993436013. The cubic root of 51378781 is about 371.7588066337.

The spelling of 51378781 in words is "fifty-one million, three hundred seventy-eight thousand, seven hundred eighty-one".