21540236650020 has 288 divisors, whose sum is σ = 72790099200000. Its totient is φ = 5111884028160.

The previous prime is 21540236649917. The next prime is 21540236650069. The reversal of 21540236650020 is 2005663204512.

21540236650020 is a `hidden beast` number, since 2 + 1 + 54 + 0 + 23 + 66 + 500 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 27534231 + ... + 28305729.

It is an arithmetic number, because the mean of its divisors is an integer number (252743400000).

Almost surely, 2^{21540236650020} is an apocalyptic number.

21540236650020 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 21540236650020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36395049600000).

21540236650020 is an abundant number, since it is smaller than the sum of its proper divisors (51249862549980).

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

21540236650020 is a wasteful number, since it uses less digits than its factorization.

21540236650020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 771823 (or 771818 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 36.

Adding to 21540236650020 its reverse (2005663204512), we get a palindrome (23545899854532).

The spelling of 21540236650020 in words is "twenty-one trillion, five hundred forty billion, two hundred thirty-six million, six hundred fifty thousand, twenty".