51811209 has 6 divisors (see below), whose sum is σ = 74838426. Its totient is φ = 34540800.

The previous prime is 51811183. The next prime is 51811213. The reversal of 51811209 is 90211815.

It can be written as a sum of positive squares in only one way, i.e., 51796809 + 14400 = 7197^2 + 120^2 .

It is not a de Polignac number, because 51811209 - 2¹⁷ = 51680137 is a prime.

It is not an unprimeable number, because it can be changed into a prime (51815209) 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, 2878392 + ... + 2878409.

It is an arithmetic number, because the mean of its divisors is an integer number (12473071).

Almost surely, 2^51811209 is an apocalyptic number.

It is an amenable number.

51811209 is a deficient number, since it is larger than the sum of its proper divisors (23027217).

51811209 is a wasteful number, since it uses less digits than its factorization.

51811209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5756807 (or 5756804 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 27.

The square root of 51811209 is about 7198.0003473187. Note that the first 3 decimals coincide. The cubic root of 51811209 is about 372.7988598983.

The spelling of 51811209 in words is "fifty-one million, eight hundred eleven thousand, two hundred nine".