21005994240 has 1296 divisors, whose sum is σ = 98146339200. Its totient is φ = 4087480320.

The previous prime is 21005994203. The next prime is 21005994263. The reversal of 21005994240 is 4249950012.

21005994240 is a `hidden beast` number, since 21 + 0 + 0 + 599 + 4 + 2 + 40 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 21005994195 and 21005994204.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 105557661 + ... + 105557859.

It is an arithmetic number, because the mean of its divisors is an integer number (75730200).

Almost surely, 2^21005994240 is an apocalyptic number.

21005994240 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 21005994240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49073169600).

21005994240 is an abundant number, since it is smaller than the sum of its proper divisors (77140344960).

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

21005994240 is a wasteful number, since it uses less digits than its factorization.

21005994240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268 (or 244 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The spelling of 21005994240 in words is "twenty-one billion, five million, nine hundred ninety-four thousand, two hundred forty".