51021281 has 4 divisors (see below), whose sum is σ = 51667200. Its totient is φ = 50375364.

The previous prime is 51021241. The next prime is 51021307. The reversal of 51021281 is 18212015.

It is a happy number.

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 a de Polignac number, because none of the positive numbers 2^k-51021281 is a prime.

It is a super-2 number, since 2×51021281² = 5206342229761922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51021241) 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, 322841 + ... + 322998.

It is an arithmetic number, because the mean of its divisors is an integer number (12916800).

Almost surely, 2^51021281 is an apocalyptic number.

It is an amenable number.

51021281 is a deficient number, since it is larger than the sum of its proper divisors (645919).

51021281 is an equidigital number, since it uses as much as digits as its factorization.

51021281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 645918.

The product of its (nonzero) digits is 160, while the sum is 20.

The square root of 51021281 is about 7142.9182411673. The cubic root of 51021281 is about 370.8945508609.

Adding to 51021281 its reverse (18212015), we get a palindrome (69233296).

The spelling of 51021281 in words is "fifty-one million, twenty-one thousand, two hundred eighty-one".