21247552720 has 80 divisors (see below), whose sum is σ = 52005100032. Its totient is φ = 8057477120.

The previous prime is 21247552691. The next prime is 21247552721. The reversal of 21247552720 is 2725574212.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21247552720.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21247552721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 156825 + ... + 259015.

Almost surely, 2^21247552720 is an apocalyptic number.

21247552720 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 21247552720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26002550016).

21247552720 is an abundant number, since it is smaller than the sum of its proper divisors (30757547312).

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

21247552720 is a wasteful number, since it uses less digits than its factorization.

21247552720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102340 (or 102334 counting only the distinct ones).

The product of its (nonzero) digits is 78400, while the sum is 37.

The spelling of 21247552720 in words is "twenty-one billion, two hundred forty-seven million, five hundred fifty-two thousand, seven hundred twenty".