21512501005500 has 384 divisors, whose sum is σ = 72177460992000. Its totient is φ = 5525589484800.

The previous prime is 21512501005487. The next prime is 21512501005517. The reversal of 21512501005500 is 550010521512.

21512501005500 is a `hidden beast` number, since 2 + 1 + 5 + 1 + 2 + 5 + 0 + 100 + 550 + 0 = 666.

It is a super-2 number, since 2×21512501005500² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 163972929 + ... + 164104071.

It is an arithmetic number, because the mean of its divisors is an integer number (187962138000).

Almost surely, 2^{21512501005500} is an apocalyptic number.

21512501005500 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 21512501005500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36088730496000).

21512501005500 is an abundant number, since it is smaller than the sum of its proper divisors (50664959986500).

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

21512501005500 is a wasteful number, since it uses less digits than its factorization.

21512501005500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131619 (or 131601 counting only the distinct ones).

The product of its (nonzero) digits is 2500, while the sum is 27.

The spelling of 21512501005500 in words is "twenty-one trillion, five hundred twelve billion, five hundred one million, five thousand, five hundred".