21010240420 has 24 divisors (see below), whose sum is σ = 47515467384. Its totient is φ = 7757627136.

The previous prime is 21010240393. The next prime is 21010240423. The reversal of 21010240420 is 2404201012.

It can be written as a sum of positive squares in 4 ways, for example, as 980065636 + 20030174784 = 31306^2 + 141528^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21010240394 and 21010240403.

It is not an unprimeable number, because it can be changed into a prime (21010240423) 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, 40404049 + ... + 40404568.

It is an arithmetic number, because the mean of its divisors is an integer number (1979811141).

Almost surely, 2^21010240420 is an apocalyptic number.

21010240420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21010240420 is an abundant number, since it is smaller than the sum of its proper divisors (26505226964).

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

21010240420 is a wasteful number, since it uses less digits than its factorization.

21010240420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80808639 (or 80808637 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

Adding to 21010240420 its reverse (2404201012), we get a palindrome (23414441432).

The spelling of 21010240420 in words is "twenty-one billion, ten million, two hundred forty thousand, four hundred twenty".