21222121520 has 80 divisors (see below), whose sum is σ = 51257344320. Its totient is φ = 8165068800.

The previous prime is 21222121499. The next prime is 21222121541. The reversal of 21222121520 is 2512122212.

It is an interprime number because it is at equal distance from previous prime (21222121499) and next prime (21222121541).

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×21222121520² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21222121492 and 21222121501.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 187316 + ... + 278444.

It is an arithmetic number, because the mean of its divisors is an integer number (640716804).

Almost surely, 2^21222121520 is an apocalyptic number.

21222121520 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 21222121520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25628672160).

21222121520 is an abundant number, since it is smaller than the sum of its proper divisors (30035222800).

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

21222121520 is a wasteful number, since it uses less digits than its factorization.

21222121520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91254 (or 91248 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

Adding to 21222121520 its reverse (2512122212), we get a palindrome (23734243732).

The spelling of 21222121520 in words is "twenty-one billion, two hundred twenty-two million, one hundred twenty-one thousand, five hundred twenty".