21549205440 has 448 divisors, whose sum is σ = 91995955200. Its totient is φ = 4635574272.

The previous prime is 21549205399. The next prime is 21549205463. The reversal of 21549205440 is 4450294512.

It is a happy number.

21549205440 is a `hidden beast` number, since 2 + 1 + 5 + 4 + 9 + 205 + 440 = 666.

It is a tau number, because it is divible by the number of its divisors (448).

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 = 21549205395 and 21549205404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1017681 + ... + 1038639.

Almost surely, 2^21549205440 is an apocalyptic number.

21549205440 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 21549205440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45997977600).

21549205440 is an abundant number, since it is smaller than the sum of its proper divisors (70446749760).

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

21549205440 is a wasteful number, since it uses less digits than its factorization.

21549205440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21009 (or 20993 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 36.

Adding to 21549205440 its reverse (4450294512), we get a palindrome (25999499952).

The spelling of 21549205440 in words is "twenty-one billion, five hundred forty-nine million, two hundred five thousand, four hundred forty".