21021111557220 has 24 divisors (see below), whose sum is σ = 58859112360384. Its totient is φ = 5605629748576.

The previous prime is 21021111557209. The next prime is 21021111557227. The reversal of 21021111557220 is 2275511112012.

It is a super-2 number, since 2×21021111557220² (a number of 27 digits) contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (21021111557227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175175929584 + ... + 175175929703.

It is an arithmetic number, because the mean of its divisors is an integer number (2452463015016).

Almost surely, 2^{21021111557220} is an apocalyptic number.

21021111557220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021111557220 is an abundant number, since it is smaller than the sum of its proper divisors (37838000803164).

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

21021111557220 is a wasteful number, since it uses less digits than its factorization.

21021111557220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350351859299 (or 350351859297 counting only the distinct ones).

The product of its (nonzero) digits is 2800, while the sum is 30.

Adding to 21021111557220 its reverse (2275511112012), we get a palindrome (23296622669232).

The spelling of 21021111557220 in words is "twenty-one trillion, twenty-one billion, one hundred eleven million, five hundred fifty-seven thousand, two hundred twenty".