21253212656561 has 8 divisors (see below), whose sum is σ = 22372526462400. Its totient is φ = 20133971217360.

The previous prime is 21253212656539. The next prime is 21253212656593. The reversal of 21253212656561 is 16565621235212.

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 21253212656561 - 2³⁰ = 21252138914737 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253212656161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17488301 + ... + 18664058.

It is an arithmetic number, because the mean of its divisors is an integer number (2796565807800).

Almost surely, 2^{21253212656561} is an apocalyptic number.

It is an amenable number.

21253212656561 is a deficient number, since it is larger than the sum of its proper divisors (1119313805839).

21253212656561 is a wasteful number, since it uses less digits than its factorization.

21253212656561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36183319.

The product of its digits is 1296000, while the sum is 47.

The spelling of 21253212656561 in words is "twenty-one trillion, two hundred fifty-three billion, two hundred twelve million, six hundred fifty-six thousand, five hundred sixty-one".