21041666661 has 8 divisors (see below), whose sum is σ = 28056261600. Its totient is φ = 14027424752.

The previous prime is 21041666651. The next prime is 21041666689. The reversal of 21041666661 is 16666614012.

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 21041666661 - 2⁵ = 21041666629 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21041666651) 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, 123190 + ... + 239288.

It is an arithmetic number, because the mean of its divisors is an integer number (3507032700).

Almost surely, 2^21041666661 is an apocalyptic number.

It is an amenable number.

21041666661 is a deficient number, since it is larger than the sum of its proper divisors (7014594939).

21041666661 is a wasteful number, since it uses less digits than its factorization.

21041666661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176515.

The product of its (nonzero) digits is 62208, while the sum is 39.

The spelling of 21041666661 in words is "twenty-one billion, forty-one million, six hundred sixty-six thousand, six hundred sixty-one".