51690821 has 16 divisors (see below), whose sum is σ = 66388224. Its totient is φ = 39118464.

The previous prime is 51690797. The next prime is 51690839. The reversal of 51690821 is 12809615.

51690821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 51690821 - 2⁶ = 51690757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51690841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10256 + ... + 14441.

It is an arithmetic number, because the mean of its divisors is an integer number (4149264).

Almost surely, 2^51690821 is an apocalyptic number.

It is an amenable number.

51690821 is a deficient number, since it is larger than the sum of its proper divisors (14697403).

51690821 is a wasteful number, since it uses less digits than its factorization.

51690821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24740.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 51690821 is about 7189.6328835345. The cubic root of 51690821 is about 372.5098920845.

The spelling of 51690821 in words is "fifty-one million, six hundred ninety thousand, eight hundred twenty-one".