21020001220 has 24 divisors (see below), whose sum is σ = 46738591704. Its totient is φ = 7913412096.

The previous prime is 21020001209. The next prime is 21020001227. The reversal of 21020001220 is 2210002012.

It can be written as a sum of positive squares in 4 ways, for example, as 343286784 + 20676714436 = 18528^2 + 143794^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21020001197 and 21020001206.

It is not an unprimeable number, because it can be changed into a prime (21020001227) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 30911427 + ... + 30912106.

It is an arithmetic number, because the mean of its divisors is an integer number (1947441321).

Almost surely, 2^21020001220 is an apocalyptic number.

21020001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21020001220 is an abundant number, since it is smaller than the sum of its proper divisors (25718590484).

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

21020001220 is a wasteful number, since it uses less digits than its factorization.

21020001220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61823559 (or 61823557 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21020001220 its reverse (2210002012), we get a palindrome (23230003232).

The spelling of 21020001220 in words is "twenty-one billion, twenty million, one thousand, two hundred twenty".