51681569 has 4 divisors (see below), whose sum is σ = 51697044. Its totient is φ = 51666096.

The previous prime is 51681541. The next prime is 51681601. The reversal of 51681569 is 96518615.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 96518615 = 5 ⋅19303723.

It can be written as a sum of positive squares in 2 ways, for example, as 6630625 + 45050944 = 2575^2 + 6712^2 .

It is a cyclic number.

It is not a de Polignac number, because 51681569 - 2²⁰ = 50632993 is a prime.

It is a super-2 number, since 2×51681569² = 5341969148603522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51681169) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 422 + ... + 10175.

It is an arithmetic number, because the mean of its divisors is an integer number (12924261).

Almost surely, 2^51681569 is an apocalyptic number.

It is an amenable number.

51681569 is a deficient number, since it is larger than the sum of its proper divisors (15475).

51681569 is a wasteful number, since it uses less digits than its factorization.

51681569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15474.

The product of its digits is 64800, while the sum is 41.

The square root of 51681569 is about 7188.9894282855. The cubic root of 51681569 is about 372.4876659129.

The spelling of 51681569 in words is "fifty-one million, six hundred eighty-one thousand, five hundred sixty-nine".