21284646805 has 4 divisors (see below), whose sum is σ = 25541576172. Its totient is φ = 17027717440.

The previous prime is 21284646793. The next prime is 21284646829. The reversal of 21284646805 is 50864648212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13145539716 + 8139107089 = 114654^2 + 90217^2 .

It is not a de Polignac number, because 21284646805 - 2⁹ = 21284646293 is a prime.

It is a super-2 number, since 2×21284646805² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2128464676 + ... + 2128464685.

It is an arithmetic number, because the mean of its divisors is an integer number (6385394043).

Almost surely, 2^21284646805 is an apocalyptic number.

It is an amenable number.

21284646805 is a deficient number, since it is larger than the sum of its proper divisors (4256929367).

21284646805 is an equidigital number, since it uses as much as digits as its factorization.

21284646805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4256929366.

The product of its (nonzero) digits is 737280, while the sum is 46.

The spelling of 21284646805 in words is "twenty-one billion, two hundred eighty-four million, six hundred forty-six thousand, eight hundred five".