21264561305 has 8 divisors (see below), whose sum is σ = 27480356232. Its totient is φ = 15703060608.

The previous prime is 21264561211. The next prime is 21264561343. The reversal of 21264561305 is 50316546212.

It can be written as a sum of positive squares in 4 ways, for example, as 958026304 + 20306535001 = 30952^2 + 142501^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21264561305 - 2¹⁴ = 21264544921 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 163573484 + ... + 163573613.

It is an arithmetic number, because the mean of its divisors is an integer number (3435044529).

Almost surely, 2^21264561305 is an apocalyptic number.

It is an amenable number.

21264561305 is a deficient number, since it is larger than the sum of its proper divisors (6215794927).

21264561305 is a wasteful number, since it uses less digits than its factorization.

21264561305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 327147115.

The product of its (nonzero) digits is 43200, while the sum is 35.

The spelling of 21264561305 in words is "twenty-one billion, two hundred sixty-four million, five hundred sixty-one thousand, three hundred five".