21263666165604 has 18 divisors (see below), whose sum is σ = 53749822807590. Its totient is φ = 7087888721856.

The previous prime is 21263666165597. The next prime is 21263666165611. The reversal of 21263666165604 is 40656166636212.

It is an interprime number because it is at equal distance from previous prime (21263666165597) and next prime (21263666165611).

It can be written as a sum of positive squares in only one way, i.e., 20231914040100 + 1031752125504 = 4497990^2 + 1015752^2 .

It is a tau number, because it is divible by the number of its divisors (18).

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 5 ways as a sum of consecutive naturals, for example, 295328696709 + ... + 295328696780.

Almost surely, 2^{21263666165604} is an apocalyptic number.

It is an amenable number.

21263666165604 is an abundant number, since it is smaller than the sum of its proper divisors (32486156641986).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21263666165604 is a wasteful number, since it uses less digits than its factorization.

21263666165604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 590657393499 (or 590657393494 counting only the distinct ones).

The product of its (nonzero) digits is 11197440, while the sum is 54.

The spelling of 21263666165604 in words is "twenty-one trillion, two hundred sixty-three billion, six hundred sixty-six million, one hundred sixty-five thousand, six hundred four".