21663011555531 has 4 divisors (see below), whose sum is σ = 21674230103064. Its totient is φ = 21651793008000.

The previous prime is 21663011555503. The next prime is 21663011555539. The reversal of 21663011555531 is 13555511036612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21663011555531 - 2²² = 21663007361227 is a prime.

It is a super-2 number, since 2×21663011555531² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21663011555539) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 5609270870 + ... + 5609274731.

It is an arithmetic number, because the mean of its divisors is an integer number (5418557525766).

Almost surely, 2^{21663011555531} is an apocalyptic number.

21663011555531 is a deficient number, since it is larger than the sum of its proper divisors (11218547533).

21663011555531 is a wasteful number, since it uses less digits than its factorization.

21663011555531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11218547532.

The product of its (nonzero) digits is 405000, while the sum is 44.

The spelling of 21663011555531 in words is "twenty-one trillion, six hundred sixty-three billion, eleven million, five hundred fifty-five thousand, five hundred thirty-one".