51021121620 has 144 divisors (see below), whose sum is σ = 167829435648. Its totient is φ = 11546438400.

The previous prime is 51021121603. The next prime is 51021121649. The reversal of 51021121620 is 2612112015.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 211029 + ... + 382851.

It is an arithmetic number, because the mean of its divisors is an integer number (1165482192).

Almost surely, 2^51021121620 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 51021121620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (83914717824).

51021121620 is an abundant number, since it is smaller than the sum of its proper divisors (116808314028).

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

51021121620 is a wasteful number, since it uses less digits than its factorization.

51021121620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171950 (or 171941 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 21.

Adding to 51021121620 its reverse (2612112015), we get a palindrome (53633233635).

The spelling of 51021121620 in words is "fifty-one billion, twenty-one million, one hundred twenty-one thousand, six hundred twenty".