21044069865 has 256 divisors, whose sum is σ = 48064880640. Its totient is φ = 8498856960.

The previous prime is 21044069843. The next prime is 21044069881. The reversal of 21044069865 is 56896044012.

It is not a de Polignac number, because 21044069865 - 2⁵ = 21044069833 is a prime.

It is a super-2 number, since 2×21044069865² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21044069865.

It is an unprimeable number.

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 255 ways as a sum of consecutive naturals, for example, 30454170 + ... + 30454860.

It is an arithmetic number, because the mean of its divisors is an integer number (187753440).

Almost surely, 2^21044069865 is an apocalyptic number.

It is an amenable number.

21044069865 is an abundant number, since it is smaller than the sum of its proper divisors (27020810775).

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

21044069865 is a wasteful number, since it uses less digits than its factorization.

21044069865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 829 (or 823 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 45.

The spelling of 21044069865 in words is "twenty-one billion, forty-four million, sixty-nine thousand, eight hundred sixty-five".