21285663720 has 128 divisors (see below), whose sum is σ = 66722745600. Its totient is φ = 5422106624.

The previous prime is 21285663683. The next prime is 21285663731. The reversal of 21285663720 is 2736658212.

It is a super-3 number, since 3×21285663720³ (a number of 32 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2228074 + ... + 2237606.

It is an arithmetic number, because the mean of its divisors is an integer number (521271450).

Almost surely, 2^21285663720 is an apocalyptic number.

21285663720 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 21285663720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33361372800).

21285663720 is an abundant number, since it is smaller than the sum of its proper divisors (45437081880).

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

21285663720 is a wasteful number, since it uses less digits than its factorization.

21285663720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10379 (or 10375 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 42.

The spelling of 21285663720 in words is "twenty-one billion, two hundred eighty-five million, six hundred sixty-three thousand, seven hundred twenty".