21220400320 has 112 divisors (see below), whose sum is σ = 57820730688. Its totient is φ = 7266631680.

The previous prime is 21220400291. The next prime is 21220400351. The reversal of 21220400320 is 2300402212.

It is a tau number, because it is divible by the number of its divisors (112).

It is a super-2 number, since 2×21220400320² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a junction number, because it is equal to n+sod(n) for n = 21220400294 and 21220400303.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1968064 + ... + 1978816.

It is an arithmetic number, because the mean of its divisors is an integer number (516256524).

Almost surely, 2^21220400320 is an apocalyptic number.

21220400320 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 21220400320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28910365344).

21220400320 is an abundant number, since it is smaller than the sum of its proper divisors (36600330368).

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

21220400320 is a wasteful number, since it uses less digits than its factorization.

21220400320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11658 (or 11648 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

Adding to 21220400320 its reverse (2300402212), we get a palindrome (23520802532).

The spelling of 21220400320 in words is "twenty-one billion, two hundred twenty million, four hundred thousand, three hundred twenty".