21421020420 has 72 divisors (see below), whose sum is σ = 65061576216. Its totient is φ = 5704845312.

The previous prime is 21421020373. The next prime is 21421020427. The reversal of 21421020420 is 2402012412.

21421020420 is a `hidden beast` number, since 2 + 14 + 210 + 20 + 420 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 3339915264 + 18081105156 = 57792^2 + 134466^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21421020393 and 21421020402.

It is not an unprimeable number, because it can be changed into a prime (21421020427) 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 23 ways as a sum of consecutive naturals, for example, 62164 + ... + 216116.

It is an arithmetic number, because the mean of its divisors is an integer number (903633003).

Almost surely, 2^21421020420 is an apocalyptic number.

21421020420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21421020420 is an abundant number, since it is smaller than the sum of its proper divisors (43640555796).

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

21421020420 is a wasteful number, since it uses less digits than its factorization.

21421020420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154741 (or 154736 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

Adding to 21421020420 its reverse (2402012412), we get a palindrome (23823032832).

The spelling of 21421020420 in words is "twenty-one billion, four hundred twenty-one million, twenty thousand, four hundred twenty".