51217561721 has 4 divisors (see below), whose sum is σ = 51220143744. Its totient is φ = 51214979700.

The previous prime is 51217561711. The next prime is 51217561729. The reversal of 51217561721 is 12716571215.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 51217561721 - 2⁶ = 51217561657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51217561729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1261025 + ... + 1301006.

It is an arithmetic number, because the mean of its divisors is an integer number (12805035936).

Almost surely, 2^51217561721 is an apocalyptic number.

It is an amenable number.

51217561721 is a deficient number, since it is larger than the sum of its proper divisors (2582023).

51217561721 is a wasteful number, since it uses less digits than its factorization.

51217561721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2582022.

The product of its digits is 29400, while the sum is 38.

The spelling of 51217561721 in words is "fifty-one billion, two hundred seventeen million, five hundred sixty-one thousand, seven hundred twenty-one".