21515531221020 has 24 divisors (see below), whose sum is σ = 60243487419024. Its totient is φ = 5737474992256.

The previous prime is 21515531220991. The next prime is 21515531221021. The reversal of 21515531221020 is 2012213551512.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21515531221021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 179296093449 + ... + 179296093568.

It is an arithmetic number, because the mean of its divisors is an integer number (2510145309126).

Almost surely, 2^{21515531221020} is an apocalyptic number.

21515531221020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21515531221020 is an abundant number, since it is smaller than the sum of its proper divisors (38727956198004).

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

21515531221020 is a wasteful number, since it uses less digits than its factorization.

21515531221020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 358592187029 (or 358592187027 counting only the distinct ones).

The product of its (nonzero) digits is 6000, while the sum is 30.

Adding to 21515531221020 its reverse (2012213551512), we get a palindrome (23527744772532).

The spelling of 21515531221020 in words is "twenty-one trillion, five hundred fifteen billion, five hundred thirty-one million, two hundred twenty-one thousand, twenty".