21110651661 has 32 divisors (see below), whose sum is σ = 31552230528. Its totient is φ = 12442256640.

The previous prime is 21110651633. The next prime is 21110651669. The reversal of 21110651661 is 16615601112.

It is not a de Polignac number, because 21110651661 - 2¹⁰ = 21110650637 is a prime.

It is a super-2 number, since 2×21110651661² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21110651669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3705331 + ... + 3711023.

It is an arithmetic number, because the mean of its divisors is an integer number (986007204).

Almost surely, 2^21110651661 is an apocalyptic number.

It is an amenable number.

21110651661 is a deficient number, since it is larger than the sum of its proper divisors (10441578867).

21110651661 is a wasteful number, since it uses less digits than its factorization.

21110651661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8781.

The product of its (nonzero) digits is 2160, while the sum is 30.

The spelling of 21110651661 in words is "twenty-one billion, one hundred ten million, six hundred fifty-one thousand, six hundred sixty-one".