51730721281 has 4 divisors (see below), whose sum is σ = 51731178052. Its totient is φ = 51730264512.

The previous prime is 51730721261. The next prime is 51730721291. The reversal of 51730721281 is 18212703715.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 18212703715 = 5 ⋅3642540743.

It can be written as a sum of positive squares in 2 ways, for example, as 21751530256 + 29979191025 = 147484^2 + 173145^2 .

It is a cyclic number.

It is not a de Polignac number, because 51730721281 - 2⁵ = 51730721249 is a prime.

It is a super-2 number, since 2×51730721281² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 51730721281.

It is not an unprimeable number, because it can be changed into a prime (51730721261) 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, 83125 + ... + 332221.

It is an arithmetic number, because the mean of its divisors is an integer number (12932794513).

Almost surely, 2^51730721281 is an apocalyptic number.

It is an amenable number.

51730721281 is a deficient number, since it is larger than the sum of its proper divisors (456771).

51730721281 is a wasteful number, since it uses less digits than its factorization.

51730721281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 456770.

The product of its (nonzero) digits is 23520, while the sum is 37.

The spelling of 51730721281 in words is "fifty-one billion, seven hundred thirty million, seven hundred twenty-one thousand, two hundred eighty-one".