51855809 has 2 divisors, whose sum is σ = 51855810. Its totient is φ = 51855808.

The previous prime is 51855803. The next prime is 51855821. The reversal of 51855809 is 90855815.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50367409 + 1488400 = 7097^2 + 1220^2 .

It is a cyclic number.

It is not a de Polignac number, because 51855809 - 2⁸ = 51855553 is a prime.

It is not a weakly prime, because it can be changed into another prime (51855803) by changing a digit.

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 as a sum of consecutive naturals, namely, 25927904 + 25927905.

It is an arithmetic number, because the mean of its divisors is an integer number (25927905).

Almost surely, 2^51855809 is an apocalyptic number.

It is an amenable number.

51855809 is a deficient number, since it is larger than the sum of its proper divisors (1).

51855809 is an equidigital number, since it uses as much as digits as its factorization.

51855809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72000, while the sum is 41.

The square root of 51855809 is about 7201.0977635358. The cubic root of 51855809 is about 372.9057998241.

The spelling of 51855809 in words is "fifty-one million, eight hundred fifty-five thousand, eight hundred nine".