21564345840 has 60 divisors (see below), whose sum is σ = 66856525224. Its totient is φ = 5749885568.

The previous prime is 21564345839. The next prime is 21564345841. The reversal of 21564345840 is 4854346512.

It is an interprime number because it is at equal distance from previous prime (21564345839) and next prime (21564345841).

It is a tau number, because it is divible by the number of its divisors (60).

It is a junction number, because it is equal to n+sod(n) for n = 21564345792 and 21564345801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21564345841) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 2270221 + ... + 2279699.

Almost surely, 2^21564345840 is an apocalyptic number.

21564345840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21564345840 is an abundant number, since it is smaller than the sum of its proper divisors (45292179384).

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

21564345840 is an frugal number, since it uses more digits than its factorization.

21564345840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18974 (or 9489 counting only the distinct ones).

The product of its (nonzero) digits is 460800, while the sum is 42.

The spelling of 21564345840 in words is "twenty-one billion, five hundred sixty-four million, three hundred forty-five thousand, eight hundred forty".