51021900 has 90 divisors (see below), whose sum is σ = 165419100. Its totient is φ = 13603680.

The previous prime is 51021851. The next prime is 51021911. The reversal of 51021900 is 912015.

It is a tau number, because it is divible by the number of its divisors (90).

It is a super-2 number, since 2×51021900² = 5206468559220000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 4951 + ... + 11249.

It is an arithmetic number, because the mean of its divisors is an integer number (1837990).

Almost surely, 2^51021900 is an apocalyptic number.

51021900 is a gapful number since it is divisible by the number (50) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 51021900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (82709550).

51021900 is an abundant number, since it is smaller than the sum of its proper divisors (114397200).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

51021900 is a wasteful number, since it uses less digits than its factorization.

51021900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6325 (or 6309 counting only the distinct ones).

The product of its (nonzero) digits is 90, while the sum is 18.

The square root of 51021900 is about 7142.9615706652. The cubic root of 51021900 is about 370.8960507762.

Adding to 51021900 its reverse (912015), we get a palindrome (51933915).

The spelling of 51021900 in words is "fifty-one million, twenty-one thousand, nine hundred".