21351216560 has 240 divisors, whose sum is σ = 54758280960. Its totient is φ = 7718699520.

The previous prime is 21351216533. The next prime is 21351216583. The reversal of 21351216560 is 6561215312.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 199544027 + ... + 199544133.

It is an arithmetic number, because the mean of its divisors is an integer number (228159504).

Almost surely, 2^21351216560 is an apocalyptic number.

21351216560 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 21351216560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27379140480).

21351216560 is an abundant number, since it is smaller than the sum of its proper divisors (33407064400).

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

21351216560 is a wasteful number, since it uses less digits than its factorization.

21351216560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296 (or 247 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 32.

The spelling of 21351216560 in words is "twenty-one billion, three hundred fifty-one million, two hundred sixteen thousand, five hundred sixty".