21531510013500 has 144 divisors (see below), whose sum is σ = 67930359745248. Its totient is φ = 5741260704000.

The previous prime is 21531510013477. The next prime is 21531510013513. The reversal of 21531510013500 is 531001513512.

21531510013500 is a `hidden beast` number, since 2 + 1 + 5 + 3 + 151 + 0 + 0 + 1 + 3 + 500 = 666.

It is a super-2 number, since 2×21531510013500² (a number of 27 digits) contains 22 as substring.

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, 55936695 + ... + 56320305.

It is an arithmetic number, because the mean of its divisors is an integer number (471738609342).

Almost surely, 2^{21531510013500} is an apocalyptic number.

21531510013500 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 21531510013500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33965179872624).

21531510013500 is an abundant number, since it is smaller than the sum of its proper divisors (46398849731748).

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

21531510013500 is a wasteful number, since it uses less digits than its factorization.

21531510013500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396109 (or 396094 counting only the distinct ones).

The product of its (nonzero) digits is 2250, while the sum is 27.

The spelling of 21531510013500 in words is "twenty-one trillion, five hundred thirty-one billion, five hundred ten million, thirteen thousand, five hundred".