21106665550 has 12 divisors (see below), whose sum is σ = 39258398016. Its totient is φ = 8442666200.

The previous prime is 21106665539. The next prime is 21106665557. The reversal of 21106665550 is 5556660112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21106665557) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 211066606 + ... + 211066705.

It is an arithmetic number, because the mean of its divisors is an integer number (3271533168).

Almost surely, 2^21106665550 is an apocalyptic number.

21106665550 is a deficient number, since it is larger than the sum of its proper divisors (18151732466).

21106665550 is a wasteful number, since it uses less digits than its factorization.

21106665550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 422133323 (or 422133318 counting only the distinct ones).

The product of its (nonzero) digits is 54000, while the sum is 37.

The spelling of 21106665550 in words is "twenty-one billion, one hundred six million, six hundred sixty-five thousand, five hundred fifty".