21131515555220 has 192 divisors, whose sum is σ = 53868377203200. Its totient is φ = 6808859688960.

The previous prime is 21131515555181. The next prime is 21131515555247. The reversal of 21131515555220 is 2255551513112.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 71930591 + ... + 72223769.

It is an arithmetic number, because the mean of its divisors is an integer number (280564464600).

Almost surely, 2^{21131515555220} is an apocalyptic number.

21131515555220 is a gapful number since it is divisible by the number (20) 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 21131515555220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26934188601600).

21131515555220 is an abundant number, since it is smaller than the sum of its proper divisors (32736861647980).

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

21131515555220 is a wasteful number, since it uses less digits than its factorization.

21131515555220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293698 (or 293696 counting only the distinct ones).

The product of its (nonzero) digits is 75000, while the sum is 38.

The spelling of 21131515555220 in words is "twenty-one trillion, one hundred thirty-one billion, five hundred fifteen million, five hundred fifty-five thousand, two hundred twenty".