21355515124240 has 160 divisors (see below), whose sum is σ = 54486818870400. Its totient is φ = 7719659458560.

The previous prime is 21355515124201. The next prime is 21355515124241. The reversal of 21355515124240 is 4242151555312.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 21355515124193 and 21355515124202.

It is not an unprimeable number, because it can be changed into a prime (21355515124241) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 129494956 + ... + 129659764.

It is an arithmetic number, because the mean of its divisors is an integer number (340542617940).

Almost surely, 2^{21355515124240} is an apocalyptic number.

21355515124240 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 21355515124240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27243409435200).

21355515124240 is an abundant number, since it is smaller than the sum of its proper divisors (33131303746160).

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

21355515124240 is a wasteful number, since it uses less digits than its factorization.

21355515124240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165705 (or 165699 counting only the distinct ones).

The product of its (nonzero) digits is 240000, while the sum is 40.

Adding to 21355515124240 its reverse (4242151555312), we get a palindrome (25597666679552).

The spelling of 21355515124240 in words is "twenty-one trillion, three hundred fifty-five billion, five hundred fifteen million, one hundred twenty-four thousand, two hundred forty".