21780635705 has 16 divisors (see below), whose sum is σ = 28087274880. Its totient is φ = 16154764032.

The previous prime is 21780635689. The next prime is 21780635711. The reversal of 21780635705 is 50753608712.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21780635705 - 2⁴ = 21780635689 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1906565 + ... + 1917954.

It is an arithmetic number, because the mean of its divisors is an integer number (1755454680).

Almost surely, 2^21780635705 is an apocalyptic number.

It is an amenable number.

21780635705 is a deficient number, since it is larger than the sum of its proper divisors (6306639175).

21780635705 is a wasteful number, since it uses less digits than its factorization.

21780635705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3824608.

The product of its (nonzero) digits is 352800, while the sum is 44.

The spelling of 21780635705 in words is "twenty-one billion, seven hundred eighty million, six hundred thirty-five thousand, seven hundred five".