51995721 has 4 divisors (see below), whose sum is σ = 69327632. Its totient is φ = 34663812.

The previous prime is 51995719. The next prime is 51995737. The reversal of 51995721 is 12759915.

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 not a de Polignac number, because 51995721 - 2¹ = 51995719 is a prime.

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 51995721.

It is not an unprimeable number, because it can be changed into a prime (51995701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8665951 + ... + 8665956.

It is an arithmetic number, because the mean of its divisors is an integer number (17331908).

Almost surely, 2^51995721 is an apocalyptic number.

It is an amenable number.

51995721 is a deficient number, since it is larger than the sum of its proper divisors (17331911).

51995721 is a wasteful number, since it uses less digits than its factorization.

51995721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17331910.

The product of its digits is 28350, while the sum is 39.

The square root of 51995721 is about 7210.8058495566. The cubic root of 51995721 is about 373.2408773142.

The spelling of 51995721 in words is "fifty-one million, nine hundred ninety-five thousand, seven hundred twenty-one".