21641543550 has 288 divisors, whose sum is σ = 66198263040. Its totient is φ = 5213030400.

The previous prime is 21641543549. The next prime is 21641543551. The reversal of 21641543550 is 5534514612.

21641543550 is a `hidden beast` number, since 2 + 1 + 64 + 1 + 5 + 43 + 550 = 666.

It is an interprime number because it is at equal distance from previous prime (21641543549) and next prime (21641543551).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21641543551) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 25794031 + ... + 25794869.

It is an arithmetic number, because the mean of its divisors is an integer number (229855080).

Almost surely, 2^21641543550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21641543550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33099131520).

21641543550 is an abundant number, since it is smaller than the sum of its proper divisors (44556719490).

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

21641543550 is a wasteful number, since it uses less digits than its factorization.

21641543550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1070 (or 1053 counting only the distinct ones).

The product of its (nonzero) digits is 72000, while the sum is 36.

The spelling of 21641543550 in words is "twenty-one billion, six hundred forty-one million, five hundred forty-three thousand, five hundred fifty".