1666225220621 has 8 divisors (see below), whose sum is σ = 1800520615320. Its totient is φ = 1532804715072.

The previous prime is 1666225220609. The next prime is 1666225220657. The reversal of 1666225220621 is 1260225226661.

It can be written as a sum of positive squares in 4 ways, for example, as 823712347396 + 842512873225 = 907586^2 + 917885^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1666225220621 - 2²² = 1666221026317 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666225229621) 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, 218718326 + ... + 218725943.

It is an arithmetic number, because the mean of its divisors is an integer number (225065076915).

Almost surely, 2^{1666225220621} is an apocalyptic number.

It is an amenable number.

1666225220621 is a deficient number, since it is larger than the sum of its proper divisors (134295394699).

1666225220621 is a wasteful number, since it uses less digits than its factorization.

1666225220621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 437444575.

The product of its (nonzero) digits is 207360, while the sum is 41.

The spelling of 1666225220621 in words is "one trillion, six hundred sixty-six billion, two hundred twenty-five million, two hundred twenty thousand, six hundred twenty-one".