21538598400 has 720 divisors, whose sum is σ = 87862769280. Its totient is φ = 4987699200.

The previous prime is 21538598387. The next prime is 21538598467. The reversal of 21538598400 is 489583512.

21538598400 is a `hidden beast` number, since 2 + 1 + 53 + 8 + 598 + 4 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (720).

It is a super-2 number, since 2×21538598400² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 29145231 + ... + 29145969.

It is an arithmetic number, because the mean of its divisors is an integer number (122031624).

Almost surely, 2^21538598400 is an apocalyptic number.

21538598400 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 21538598400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43931384640).

21538598400 is an abundant number, since it is smaller than the sum of its proper divisors (66324170880).

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

21538598400 is a wasteful number, since it uses less digits than its factorization.

21538598400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 807 (or 783 counting only the distinct ones).

The product of its (nonzero) digits is 345600, while the sum is 45.

The spelling of 21538598400 in words is "twenty-one billion, five hundred thirty-eight million, five hundred ninety-eight thousand, four hundred".