21405541640 has 64 divisors (see below), whose sum is σ = 55063532160. Its totient is φ = 7336281600.

The previous prime is 21405541627. The next prime is 21405541643. The reversal of 21405541640 is 4614550412.

It is a junction number, because it is equal to n+sod(n) for n = 21405541597 and 21405541606.

It is not an unprimeable number, because it can be changed into a prime (21405541643) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 816740 + ... + 842540.

It is an arithmetic number, because the mean of its divisors is an integer number (860367690).

Almost surely, 2^21405541640 is an apocalyptic number.

21405541640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21405541640 is an abundant number, since it is smaller than the sum of its proper divisors (33657990520).

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

21405541640 is a wasteful number, since it uses less digits than its factorization.

21405541640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28782 (or 28778 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 32.

The spelling of 21405541640 in words is "twenty-one billion, four hundred five million, five hundred forty-one thousand, six hundred forty".