51787781 has 16 divisors (see below), whose sum is σ = 54648000. Its totient is φ = 49031808.

The previous prime is 51787759. The next prime is 51787793. The reversal of 51787781 is 18778715.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 51787781 - 2¹⁸ = 51525637 is a prime.

It is a super-2 number, since 2×51787781² = 5363948521807922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51787721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 347495 + ... + 347643.

It is an arithmetic number, because the mean of its divisors is an integer number (3415500).

Almost surely, 2^51787781 is an apocalyptic number.

It is an amenable number.

51787781 is a deficient number, since it is larger than the sum of its proper divisors (2860219).

51787781 is a wasteful number, since it uses less digits than its factorization.

51787781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388.

The product of its digits is 109760, while the sum is 44.

The square root of 51787781 is about 7196.3727668875. The cubic root of 51787781 is about 372.7426606792.

The spelling of 51787781 in words is "fifty-one million, seven hundred eighty-seven thousand, seven hundred eighty-one".