51991439 has 2 divisors, whose sum is σ = 51991440. Its totient is φ = 51991438.

The previous prime is 51991369. The next prime is 51991441. The reversal of 51991439 is 93419915.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 51991439 - 2⁸ = 51991183 is a prime.

Together with 51991441, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 51991396 and 51991405.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51991469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25995719 + 25995720.

It is an arithmetic number, because the mean of its divisors is an integer number (25995720).

Almost surely, 2^51991439 is an apocalyptic number.

51991439 is a deficient number, since it is larger than the sum of its proper divisors (1).

51991439 is an equidigital number, since it uses as much as digits as its factorization.

51991439 is an evil number, because the sum of its binary digits is even.

The product of its digits is 43740, while the sum is 41.

The square root of 51991439 is about 7210.5089279468. The cubic root of 51991439 is about 373.2306312062.

The spelling of 51991439 in words is "fifty-one million, nine hundred ninety-one thousand, four hundred thirty-nine".