21365561100663 has 12 divisors (see below), whose sum is σ = 33235317267880. Its totient is φ = 13148037600336.

The previous prime is 21365561100661. The next prime is 21365561100677. The reversal of 21365561100663 is 36600116556312.

It is a happy number.

21365561100663 is a `hidden beast` number, since 2 + 1 + 36 + 556 + 1 + 1 + 0 + 0 + 6 + 63 = 666.

It is not a de Polignac number, because 21365561100663 - 2¹ = 21365561100661 is a prime.

It is a super-2 number, since 2×21365561100663² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365561100661) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 91305816553 + ... + 91305816786.

Almost surely, 2^{21365561100663} is an apocalyptic number.

21365561100663 is a deficient number, since it is larger than the sum of its proper divisors (11869756167217).

21365561100663 is a wasteful number, since it uses less digits than its factorization.

21365561100663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182611633358 (or 182611633355 counting only the distinct ones).

The product of its (nonzero) digits is 583200, while the sum is 45.

Adding to 21365561100663 its reverse (36600116556312), we get a palindrome (57965677656975).

The spelling of 21365561100663 in words is "twenty-one trillion, three hundred sixty-five billion, five hundred sixty-one million, one hundred thousand, six hundred sixty-three".