51991385 has 16 divisors (see below), whose sum is σ = 65366784. Its totient is φ = 39623232.

The previous prime is 51991369. The next prime is 51991439. The reversal of 51991385 is 58319915.

51991385 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 51991385 - 2⁴ = 51991369 is a prime.

It is a super-2 number, since 2×51991385² = 5406208228436450, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon 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 15 ways as a sum of consecutive naturals, for example, 32924 + ... + 34466.

It is an arithmetic number, because the mean of its divisors is an integer number (4085424).

Almost surely, 2^51991385 is an apocalyptic number.

It is an amenable number.

51991385 is a deficient number, since it is larger than the sum of its proper divisors (13375399).

51991385 is a wasteful number, since it uses less digits than its factorization.

51991385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1864.

The product of its digits is 48600, while the sum is 41.

The square root of 51991385 is about 7210.5051834112. The cubic root of 51991385 is about 373.2305019897.

The spelling of 51991385 in words is "fifty-one million, nine hundred ninety-one thousand, three hundred eighty-five".