21305026664665 has 8 divisors (see below), whose sum is σ = 26447619308040. Its totient is φ = 16456296458112.

The previous prime is 21305026664599. The next prime is 21305026664759. The reversal of 21305026664665 is 56646662050312.

It can be written as a sum of positive squares in 4 ways, for example, as 6364575341721 + 14940451322944 = 2522811^2 + 3865288^2 .

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 21305026664665 - 2⁹ = 21305026664153 is a prime.

It is a super-2 number, since 2×21305026664665² (a number of 27 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73465609044 + ... + 73465609333.

It is an arithmetic number, because the mean of its divisors is an integer number (3305952413505).

Almost surely, 2^{21305026664665} is an apocalyptic number.

It is an amenable number.

21305026664665 is a deficient number, since it is larger than the sum of its proper divisors (5142592643375).

21305026664665 is a wasteful number, since it uses less digits than its factorization.

21305026664665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146931218411.

The product of its (nonzero) digits is 9331200, while the sum is 52.

The spelling of 21305026664665 in words is "twenty-one trillion, three hundred five billion, twenty-six million, six hundred sixty-four thousand, six hundred sixty-five".