51991985 has 8 divisors (see below), whose sum is σ = 62595456. Its totient is φ = 41456880.

The previous prime is 51991969. The next prime is 51991997. The reversal of 51991985 is 58919915.

51991985 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 51991985 - 2⁴ = 51991969 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15401 + ... + 18470.

It is an arithmetic number, because the mean of its divisors is an integer number (7824432).

Almost surely, 2^51991985 is an apocalyptic number.

It is an amenable number.

51991985 is a deficient number, since it is larger than the sum of its proper divisors (10603471).

51991985 is a wasteful number, since it uses less digits than its factorization.

51991985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34183.

The product of its digits is 145800, while the sum is 47.

The square root of 51991985 is about 7210.5467892525. The cubic root of 51991985 is about 373.2319377240.

The spelling of 51991985 in words is "fifty-one million, nine hundred ninety-one thousand, nine hundred eighty-five".