51221539 has 4 divisors (see below), whose sum is σ = 51451456. Its totient is φ = 50991624.

The previous prime is 51221537. The next prime is 51221543. The reversal of 51221539 is 93512215.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 93512215 = 5 ⋅18702443.

It is a cyclic number.

It is not a de Polignac number, because 51221539 - 2¹ = 51221537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51221531) 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, 114624 + ... + 115069.

It is an arithmetic number, because the mean of its divisors is an integer number (12862864).

Almost surely, 2^51221539 is an apocalyptic number.

51221539 is a deficient number, since it is larger than the sum of its proper divisors (229917).

51221539 is a wasteful number, since it uses less digits than its factorization.

51221539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229916.

The product of its digits is 2700, while the sum is 28.

The square root of 51221539 is about 7156.9224531219. The cubic root of 51221539 is about 371.3791697962.

The spelling of 51221539 in words is "fifty-one million, two hundred twenty-one thousand, five hundred thirty-nine".