21521621000 has 128 divisors (see below), whose sum is σ = 55126431360. Its totient is φ = 7799328000.

The previous prime is 21521620987. The next prime is 21521621047. The reversal of 21521621000 is 12612512.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3373814 + ... + 3380186.

It is an arithmetic number, because the mean of its divisors is an integer number (430675245).

Almost surely, 2^21521621000 is an apocalyptic number.

21521621000 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 21521621000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27563215680).

21521621000 is an abundant number, since it is smaller than the sum of its proper divisors (33604810360).

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

21521621000 is a wasteful number, since it uses less digits than its factorization.

21521621000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6712 (or 6698 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 20.

The spelling of 21521621000 in words is "twenty-one billion, five hundred twenty-one million, six hundred twenty-one thousand".