21491685600 has 576 divisors, whose sum is σ = 92361088512. Its totient is φ = 4202496000.

The previous prime is 21491685559. The next prime is 21491685601. The reversal of 21491685600 is 658619412.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21491685601) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3138180 + ... + 3145020.

It is an arithmetic number, because the mean of its divisors is an integer number (160349112).

Almost surely, 2^21491685600 is an apocalyptic number.

21491685600 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 21491685600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46180544256).

21491685600 is an abundant number, since it is smaller than the sum of its proper divisors (70869402912).

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

21491685600 is a wasteful number, since it uses less digits than its factorization.

21491685600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6899 (or 6886 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 42.

The spelling of 21491685600 in words is "twenty-one billion, four hundred ninety-one million, six hundred eighty-five thousand, six hundred".