21661699809916 has 12 divisors (see below), whose sum is σ = 37908007904088. Its totient is φ = 10830840408752.

The previous prime is 21661699809857. The next prime is 21661699809917. The reversal of 21661699809916 is 61990899616612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661699809917) 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, 6195150 + ... + 9038986.

It is an arithmetic number, because the mean of its divisors is an integer number (3159000658674).

Almost surely, 2^{21661699809916} is an apocalyptic number.

It is an amenable number.

21661699809916 is a deficient number, since it is larger than the sum of its proper divisors (16246308094172).

21661699809916 is a wasteful number, since it uses less digits than its factorization.

21661699809916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4748108 (or 4748106 counting only the distinct ones).

The product of its (nonzero) digits is 136048896, while the sum is 73.

The spelling of 21661699809916 in words is "twenty-one trillion, six hundred sixty-one billion, six hundred ninety-nine million, eight hundred nine thousand, nine hundred sixteen".