21001568165606 has 16 divisors (see below), whose sum is σ = 37164065326080. Its totient is φ = 8710327810440.

The previous prime is 21001568165551. The next prime is 21001568165647. The reversal of 21001568165606 is 60656186510012.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24195354596 + ... + 24195355463.

It is an arithmetic number, because the mean of its divisors is an integer number (2322754082880).

Almost surely, 2^{21001568165606} is an apocalyptic number.

21001568165606 is a deficient number, since it is larger than the sum of its proper divisors (16162497160474).

21001568165606 is a wasteful number, since it uses less digits than its factorization.

21001568165606 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48390710099.

The product of its (nonzero) digits is 518400, while the sum is 47.

The spelling of 21001568165606 in words is "twenty-one trillion, one billion, five hundred sixty-eight million, one hundred sixty-five thousand, six hundred six".