21651404544 has 576 divisors, whose sum is σ = 84556846080. Its totient is φ = 5290721280.

The previous prime is 21651404519. The next prime is 21651404557. The reversal of 21651404544 is 44540415612.

21651404544 is a `hidden beast` number, since 2 + 1 + 65 + 140 + 454 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (576).

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 = 21651404499 and 21651404508.

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, 9046612 + ... + 9049004.

It is an arithmetic number, because the mean of its divisors is an integer number (146800080).

Almost surely, 2^21651404544 is an apocalyptic number.

21651404544 is a gapful number since it is divisible by the number (24) 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 21651404544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42278423040).

21651404544 is an abundant number, since it is smaller than the sum of its proper divisors (62905441536).

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

21651404544 is a wasteful number, since it uses less digits than its factorization.

21651404544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2453 (or 2433 counting only the distinct ones).

The product of its (nonzero) digits is 76800, while the sum is 36.

The spelling of 21651404544 in words is "twenty-one billion, six hundred fifty-one million, four hundred four thousand, five hundred forty-four".