51115721 has 4 divisors (see below), whose sum is σ = 51483600. Its totient is φ = 50747844.

The previous prime is 51115711. The next prime is 51115723. The reversal of 51115721 is 12751115.

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 51115721 - 2⁶ = 51115657 is a prime.

It is a super-2 number, since 2×51115721² = 5225633866699682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (51115723) 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, 183731 + ... + 184008.

It is an arithmetic number, because the mean of its divisors is an integer number (12870900).

Almost surely, 2^51115721 is an apocalyptic number.

It is an amenable number.

51115721 is a deficient number, since it is larger than the sum of its proper divisors (367879).

51115721 is a wasteful number, since it uses less digits than its factorization.

51115721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 367878.

The product of its digits is 350, while the sum is 23.

The square root of 51115721 is about 7149.5259283396. The cubic root of 51115721 is about 371.1232508018.

Adding to 51115721 its reverse (12751115), we get a palindrome (63866836).

The spelling of 51115721 in words is "fifty-one million, one hundred fifteen thousand, seven hundred twenty-one".