21005537280 has 936 divisors, whose sum is σ = 88354285632. Its totient is φ = 4171235328.

The previous prime is 21005537261. The next prime is 21005537291. The reversal of 21005537280 is 8273550012.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1235619832 + ... + 1235619848.

Almost surely, 2^21005537280 is an apocalyptic number.

21005537280 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 21005537280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44177142816).

21005537280 is an abundant number, since it is smaller than the sum of its proper divisors (67348748352).

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

21005537280 is a wasteful number, since it uses less digits than its factorization.

21005537280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99 (or 47 counting only the distinct ones).

The product of its (nonzero) digits is 16800, while the sum is 33.

The spelling of 21005537280 in words is "twenty-one billion, five million, five hundred thirty-seven thousand, two hundred eighty".