21605204440 has 32 divisors (see below), whose sum is σ = 48994490880. Its totient is φ = 8574031872.

The previous prime is 21605204431. The next prime is 21605204471. The reversal of 21605204440 is 4440250612.

It is a junction number, because it is equal to n+sod(n) for n = 21605204399 and 21605204408.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2121417 + ... + 2131576.

It is an arithmetic number, because the mean of its divisors is an integer number (1531077840).

Almost surely, 2^21605204440 is an apocalyptic number.

21605204440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21605204440 is an abundant number, since it is smaller than the sum of its proper divisors (27389286440).

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

21605204440 is a wasteful number, since it uses less digits than its factorization.

21605204440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4253131 (or 4253127 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 28.

The spelling of 21605204440 in words is "twenty-one billion, six hundred five million, two hundred four thousand, four hundred forty".