21125917440 has 216 divisors, whose sum is σ = 73408870080. Its totient is φ = 5609275392.

The previous prime is 21125917369. The next prime is 21125917447. The reversal of 21125917440 is 4471952112.

21125917440 is a `hidden beast` number, since 2 + 1 + 125 + 91 + 7 + 440 = 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 = 21125917395 and 21125917404.

It is not an unprimeable number, because it can be changed into a prime (21125917447) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 2749444 + ... + 2757116.

It is an arithmetic number, because the mean of its divisors is an integer number (339855880).

Almost surely, 2^21125917440 is an apocalyptic number.

21125917440 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 21125917440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36704435040).

21125917440 is an abundant number, since it is smaller than the sum of its proper divisors (52282952640).

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

21125917440 is a wasteful number, since it uses less digits than its factorization.

21125917440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7939 (or 7922 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The spelling of 21125917440 in words is "twenty-one billion, one hundred twenty-five million, nine hundred seventeen thousand, four hundred forty".