51785891 has 4 divisors (see below), whose sum is σ = 51885432. Its totient is φ = 51686352.

The previous prime is 51785879. The next prime is 51785897. The reversal of 51785891 is 19858715.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19858715 = 5 ⋅3971743.

It is a cyclic number.

It is not a de Polignac number, because 51785891 - 2²² = 47591587 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51785897) 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 in 3 ways as a sum of consecutive naturals, for example, 48986 + ... + 50031.

It is an arithmetic number, because the mean of its divisors is an integer number (12971358).

Almost surely, 2^51785891 is an apocalyptic number.

51785891 is a deficient number, since it is larger than the sum of its proper divisors (99541).

51785891 is an equidigital number, since it uses as much as digits as its factorization.

51785891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99540.

The product of its digits is 100800, while the sum is 44.

The square root of 51785891 is about 7196.2414495346. The cubic root of 51785891 is about 372.7381261978.

The spelling of 51785891 in words is "fifty-one million, seven hundred eighty-five thousand, eight hundred ninety-one".