21305505540 has 96 divisors (see below), whose sum is σ = 66050095104. Its totient is φ = 5087871360.

The previous prime is 21305505523. The next prime is 21305505589. The reversal of 21305505540 is 4550550312.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21305505498 and 21305505507.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 196684 + ... + 285123.

It is an arithmetic number, because the mean of its divisors is an integer number (688021824).

Almost surely, 2^21305505540 is an apocalyptic number.

21305505540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21305505540 is an abundant number, since it is smaller than the sum of its proper divisors (44744589564).

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

21305505540 is a wasteful number, since it uses less digits than its factorization.

21305505540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 481897 (or 481895 counting only the distinct ones).

The product of its (nonzero) digits is 15000, while the sum is 30.

The spelling of 21305505540 in words is "twenty-one billion, three hundred five million, five hundred five thousand, five hundred forty".