51278809 has 4 divisors (see below), whose sum is σ = 51454116. Its totient is φ = 51103504.

The previous prime is 51278791. The next prime is 51278813. The reversal of 51278809 is 90887215.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 50013184 + 1265625 = 7072^2 + 1125^2 .

It is a cyclic number.

It is not a de Polignac number, because 51278809 - 2¹⁹ = 50754521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51278819) 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, 87214 + ... + 87799.

It is an arithmetic number, because the mean of its divisors is an integer number (12863529).

Almost surely, 2^51278809 is an apocalyptic number.

It is an amenable number.

51278809 is a deficient number, since it is larger than the sum of its proper divisors (175307).

51278809 is a wasteful number, since it uses less digits than its factorization.

51278809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 175306.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 51278809 is about 7160.9223567918. The cubic root of 51278809 is about 371.5175293196.

The spelling of 51278809 in words is "fifty-one million, two hundred seventy-eight thousand, eight hundred nine".