51686021 has 4 divisors (see below), whose sum is σ = 53353344. Its totient is φ = 50018700.

The previous prime is 51686017. The next prime is 51686039. The reversal of 51686021 is 12068615.

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 not a de Polignac number, because 51686021 - 2² = 51686017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51686081) 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, 833615 + ... + 833676.

It is an arithmetic number, because the mean of its divisors is an integer number (13338336).

Almost surely, 2^51686021 is an apocalyptic number.

It is an amenable number.

51686021 is a deficient number, since it is larger than the sum of its proper divisors (1667323).

51686021 is a wasteful number, since it uses less digits than its factorization.

51686021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1667322.

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 51686021 is about 7189.2990618001. The cubic root of 51686021 is about 372.4983613279.

The spelling of 51686021 in words is "fifty-one million, six hundred eighty-six thousand, twenty-one".