21605162365 has 4 divisors (see below), whose sum is σ = 25926194844. Its totient is φ = 17284129888.

The previous prime is 21605162353. The next prime is 21605162393. The reversal of 21605162365 is 56326150612.

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 11215233604 + 10389928761 = 105902^2 + 101931^2 .

It is a cyclic number.

It is not a de Polignac number, because 21605162365 - 2⁷ = 21605162237 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2160516232 + ... + 2160516241.

It is an arithmetic number, because the mean of its divisors is an integer number (6481548711).

Almost surely, 2^21605162365 is an apocalyptic number.

It is an amenable number.

21605162365 is a deficient number, since it is larger than the sum of its proper divisors (4321032479).

21605162365 is an equidigital number, since it uses as much as digits as its factorization.

21605162365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4321032478.

The product of its (nonzero) digits is 64800, while the sum is 37.

The spelling of 21605162365 in words is "twenty-one billion, six hundred five million, one hundred sixty-two thousand, three hundred sixty-five".