21684251520 has 192 divisors, whose sum is σ = 75107345040. Its totient is φ = 5764792320.

The previous prime is 21684251497. The next prime is 21684251531. The reversal of 21684251520 is 2515248612.

21684251520 is a `hidden beast` number, since 2 + 1 + 6 + 84 + 2 + 51 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1935535 + ... + 1946705.

Almost surely, 2^21684251520 is an apocalyptic number.

21684251520 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 21684251520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37553672520).

21684251520 is an abundant number, since it is smaller than the sum of its proper divisors (53423093520).

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

21684251520 is a wasteful number, since it uses less digits than its factorization.

21684251520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11533 (or 11518 counting only the distinct ones).

The product of its (nonzero) digits is 38400, while the sum is 36.

The spelling of 21684251520 in words is "twenty-one billion, six hundred eighty-four million, two hundred fifty-one thousand, five hundred twenty".