21661699809858 has 16 divisors (see below), whose sum is σ = 45871834891680. Its totient is φ = 6795827391296.

The previous prime is 21661699809857. The next prime is 21661699809917. The reversal of 21661699809858 is 85890899616612.

It is a super-2 number, since 2×21661699809858² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21661699809857) 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 7 ways as a sum of consecutive naturals, for example, 106184802888 + ... + 106184803091.

It is an arithmetic number, because the mean of its divisors is an integer number (2866989680730).

Almost surely, 2^{21661699809858} is an apocalyptic number.

21661699809858 is an abundant number, since it is smaller than the sum of its proper divisors (24210135081822).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21661699809858 is a wasteful number, since it uses less digits than its factorization.

21661699809858 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212369606001.

The product of its (nonzero) digits is 806215680, while the sum is 78.

The spelling of 21661699809858 in words is "twenty-one trillion, six hundred sixty-one billion, six hundred ninety-nine million, eight hundred nine thousand, eight hundred fifty-eight".