51781805 has 4 divisors (see below), whose sum is σ = 62138172. Its totient is φ = 41425440.

The previous prime is 51781799. The next prime is 51781817. The reversal of 51781805 is 50818715.

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 6165289 + 45616516 = 2483^2 + 6754^2 .

It is not a de Polignac number, because 51781805 - 2²⁴ = 35004589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5178176 + ... + 5178185.

It is an arithmetic number, because the mean of its divisors is an integer number (15534543).

Almost surely, 2^51781805 is an apocalyptic number.

It is an amenable number.

51781805 is a deficient number, since it is larger than the sum of its proper divisors (10356367).

51781805 is a wasteful number, since it uses less digits than its factorization.

51781805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10356366.

The product of its (nonzero) digits is 11200, while the sum is 35.

The square root of 51781805 is about 7195.9575457336. The cubic root of 51781805 is about 372.7283227036.

The spelling of 51781805 in words is "fifty-one million, seven hundred eighty-one thousand, eight hundred five".