21540321405 has 24 divisors (see below), whose sum is σ = 37685505312. Its totient is φ = 11380802784.

The previous prime is 21540321391. The next prime is 21540321421. The reversal of 21540321405 is 50412304512.

21540321405 is a `hidden beast` number, since 215 + 40 + 3 + 2 + 1 + 405 = 666.

It is not a de Polignac number, because 21540321405 - 2⁵ = 21540321373 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2231979 + ... + 2241608.

It is an arithmetic number, because the mean of its divisors is an integer number (1570229388).

Almost surely, 2^21540321405 is an apocalyptic number.

It is an amenable number.

21540321405 is a deficient number, since it is larger than the sum of its proper divisors (16145183907).

21540321405 is a wasteful number, since it uses less digits than its factorization.

21540321405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4473705 (or 4473702 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

Adding to 21540321405 its reverse (50412304512), we get a palindrome (71952625917).

The spelling of 21540321405 in words is "twenty-one billion, five hundred forty million, three hundred twenty-one thousand, four hundred five".