21661367601601 has 16 divisors (see below), whose sum is σ = 26661025440000. Its totient is φ = 17138098312128.

The previous prime is 21661367601521. The next prime is 21661367601617. The reversal of 21661367601601 is 10610676316612.

It is a cyclic number.

It is not a de Polignac number, because 21661367601601 - 2²⁷ = 21661233383873 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21661367601641) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 1151101 + ... + 6681898.

It is an arithmetic number, because the mean of its divisors is an integer number (1666314090000).

Almost surely, 2^{21661367601601} is an apocalyptic number.

It is an amenable number.

21661367601601 is a deficient number, since it is larger than the sum of its proper divisors (4999657838399).

21661367601601 is a wasteful number, since it uses less digits than its factorization.

21661367601601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7863408.

The product of its (nonzero) digits is 326592, while the sum is 46.

The spelling of 21661367601601 in words is "twenty-one trillion, six hundred sixty-one billion, three hundred sixty-seven million, six hundred one thousand, six hundred one".