21661699809910 has 16 divisors (see below), whose sum is σ = 39009254311296. Its totient is φ = 8660636667648.

The previous prime is 21661699809857. The next prime is 21661699809917. The reversal of 21661699809910 is 1990899616612.

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 7 ways as a sum of consecutive naturals, for example, 505384539 + ... + 505427398.

It is an arithmetic number, because the mean of its divisors is an integer number (2438078394456).

Almost surely, 2^{21661699809910} is an apocalyptic number.

21661699809910 is a deficient number, since it is larger than the sum of its proper divisors (17347554501386).

21661699809910 is a wasteful number, since it uses less digits than its factorization.

21661699809910 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1010814087.

The product of its (nonzero) digits is 22674816, while the sum is 67.

The spelling of 21661699809910 in words is "twenty-one trillion, six hundred sixty-one billion, six hundred ninety-nine million, eight hundred nine thousand, nine hundred ten".