51781217 has 6 divisors (see below), whose sum is σ = 52063842. Its totient is φ = 51499712.

The previous prime is 51781199. The next prime is 51781229. The reversal of 51781217 is 71218715.

It can be written as a sum of positive squares in only one way, i.e., 42393121 + 9388096 = 6511^2 + 3064^2 .

It is not a de Polignac number, because 51781217 - 2¹⁰ = 51780193 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51781117) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 135008 + ... + 135390.

It is an arithmetic number, because the mean of its divisors is an integer number (8677307).

Almost surely, 2^51781217 is an apocalyptic number.

It is an amenable number.

51781217 is a deficient number, since it is larger than the sum of its proper divisors (282625).

51781217 is an frugal number, since it uses more digits than its factorization.

51781217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1119 (or 736 counting only the distinct ones).

The product of its digits is 3920, while the sum is 32.

The square root of 51781217 is about 7195.9166893454. The cubic root of 51781217 is about 372.7269118793.

The spelling of 51781217 in words is "fifty-one million, seven hundred eighty-one thousand, two hundred seventeen".