21904680661 has 4 divisors (see below), whose sum is σ = 21916777824. Its totient is φ = 21892583500.

The previous prime is 21904680647. The next prime is 21904680701. The reversal of 21904680661 is 16608640912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21904680661 - 2⁷ = 21904680533 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21904687661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6045865 + ... + 6049486.

It is an arithmetic number, because the mean of its divisors is an integer number (5479194456).

Almost surely, 2^21904680661 is an apocalyptic number.

It is an amenable number.

21904680661 is a deficient number, since it is larger than the sum of its proper divisors (12097163).

21904680661 is a wasteful number, since it uses less digits than its factorization.

21904680661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12097162.

The product of its (nonzero) digits is 124416, while the sum is 43.

The spelling of 21904680661 in words is "twenty-one billion, nine hundred four million, six hundred eighty thousand, six hundred sixty-one".