51820021 has 8 divisors (see below), whose sum is σ = 57081024. Its totient is φ = 46650720.

The previous prime is 51820009. The next prime is 51820037. The reversal of 51820021 is 12002815.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 51820021 - 2²⁵ = 18265589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51820001) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21736 + ... + 24001.

It is an arithmetic number, because the mean of its divisors is an integer number (7135128).

Almost surely, 2^51820021 is an apocalyptic number.

It is an amenable number.

51820021 is a deficient number, since it is larger than the sum of its proper divisors (5261003).

51820021 is a wasteful number, since it uses less digits than its factorization.

51820021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45851.

The product of its (nonzero) digits is 160, while the sum is 19.

The square root of 51820021 is about 7198.6124357407. The cubic root of 51820021 is about 372.8199937893.

Adding to 51820021 its reverse (12002815), we get a palindrome (63822836).

The spelling of 51820021 in words is "fifty-one million, eight hundred twenty thousand, twenty-one".