21663561260551 has 8 divisors (see below), whose sum is σ = 24936473394560. Its totient is φ = 18435178543608.

The previous prime is 21663561260531. The next prime is 21663561260623. The reversal of 21663561260551 is 15506216536612.

It is a happy number.

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 21663561260551 - 2⁷ = 21663561260423 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21663561260495 and 21663561260504.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663561260501) 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, 11132353221 + ... + 11132355166.

It is an arithmetic number, because the mean of its divisors is an integer number (3117059174320).

Almost surely, 2^{21663561260551} is an apocalyptic number.

21663561260551 is a deficient number, since it is larger than the sum of its proper divisors (3272912134009).

21663561260551 is a wasteful number, since it uses less digits than its factorization.

21663561260551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22264708533.

The product of its (nonzero) digits is 1944000, while the sum is 49.

The spelling of 21663561260551 in words is "twenty-one trillion, six hundred sixty-three billion, five hundred sixty-one million, two hundred sixty thousand, five hundred fifty-one".