21021503540 has 12 divisors (see below), whose sum is σ = 44145157476. Its totient is φ = 8408601408.

The previous prime is 21021503509. The next prime is 21021503543. The reversal of 21021503540 is 4530512012.

It can be written as a sum of positive squares in 2 ways, for example, as 3285123856 + 17736379684 = 57316^2 + 133178^2 .

It is a super-2 number, since 2×21021503540² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021503543) 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 3 ways as a sum of consecutive naturals, for example, 525537569 + ... + 525537608.

It is an arithmetic number, because the mean of its divisors is an integer number (3678763123).

Almost surely, 2^21021503540 is an apocalyptic number.

21021503540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021503540 is an abundant number, since it is smaller than the sum of its proper divisors (23123653936).

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

21021503540 is a wasteful number, since it uses less digits than its factorization.

21021503540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1051075186 (or 1051075184 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 23.

The spelling of 21021503540 in words is "twenty-one billion, twenty-one million, five hundred three thousand, five hundred forty".