21605336540 has 36 divisors (see below), whose sum is σ = 46882048248. Its totient is φ = 8363348640.

The previous prime is 21605336539. The next prime is 21605336561. The reversal of 21605336540 is 4563350612.

It is a self number, because there is not a number n which added to its sum of digits gives 21605336540.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 542834 + ... + 581273.

It is an arithmetic number, because the mean of its divisors is an integer number (1302279118).

Almost surely, 2^21605336540 is an apocalyptic number.

21605336540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21605336540 is an abundant number, since it is smaller than the sum of its proper divisors (25276711708).

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

21605336540 is a wasteful number, since it uses less digits than its factorization.

21605336540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1124178 (or 1124145 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 35.

The spelling of 21605336540 in words is "twenty-one billion, six hundred five million, three hundred thirty-six thousand, five hundred forty".