21601666754657 has 4 divisors (see below), whose sum is σ = 23565454641456. Its totient is φ = 19637878867860.

The previous prime is 21601666754557. The next prime is 21601666754693. The reversal of 21601666754657 is 75645766610612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21601666754657 - 2⁴⁰ = 20502155126881 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 21601666754657.

It is not an unprimeable number, because it can be changed into a prime (21601666754557) 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, 981893943383 + ... + 981893943404.

It is an arithmetic number, because the mean of its divisors is an integer number (5891363660364).

Almost surely, 2^{21601666754657} is an apocalyptic number.

It is an amenable number.

21601666754657 is a deficient number, since it is larger than the sum of its proper divisors (1963787886799).

21601666754657 is a wasteful number, since it uses less digits than its factorization.

21601666754657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1963787886798.

The product of its (nonzero) digits is 76204800, while the sum is 62.

The spelling of 21601666754657 in words is "twenty-one trillion, six hundred one billion, six hundred sixty-six million, seven hundred fifty-four thousand, six hundred fifty-seven".