21015244512 has 144 divisors (see below), whose sum is σ = 60225394320. Its totient is φ = 6951038976.

The previous prime is 21015244457. The next prime is 21015244513. The reversal of 21015244512 is 21544251012.

It is a happy number.

21015244512 is a `hidden beast` number, since 2 + 101 + 5 + 2 + 44 + 512 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×21015244512² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21015244513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 28437039 + ... + 28437777.

It is an arithmetic number, because the mean of its divisors is an integer number (418231905).

Almost surely, 2^21015244512 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 21015244512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30112697160).

21015244512 is an abundant number, since it is smaller than the sum of its proper divisors (39210149808).

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

21015244512 is a wasteful number, since it uses less digits than its factorization.

21015244512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1385 (or 1374 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 27.

Adding to 21015244512 its reverse (21544251012), we get a palindrome (42559495524).

The spelling of 21015244512 in words is "twenty-one billion, fifteen million, two hundred forty-four thousand, five hundred twelve".