51405021 has 12 divisors (see below), whose sum is σ = 76063260. Its totient is φ = 33433920.

The previous prime is 51405017. The next prime is 51405049. The reversal of 51405021 is 12050415.

It can be written as a sum of positive squares in 2 ways, for example, as 20602521 + 30802500 = 4539^2 + 5550^2 .

It is not a de Polignac number, because 51405021 - 2² = 51405017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 51404985 and 51405003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51405121) 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 11 ways as a sum of consecutive naturals, for example, 69286 + ... + 70023.

It is an arithmetic number, because the mean of its divisors is an integer number (6338605).

Almost surely, 2^51405021 is an apocalyptic number.

It is an amenable number.

51405021 is a deficient number, since it is larger than the sum of its proper divisors (24658239).

51405021 is a wasteful number, since it uses less digits than its factorization.

51405021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139356 (or 139353 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 51405021 is about 7169.7294928052. The cubic root of 51405021 is about 371.8220836694.

Adding to 51405021 its reverse (12050415), we get a palindrome (63455436).

The spelling of 51405021 in words is "fifty-one million, four hundred five thousand, twenty-one".