666651021169 has 45 divisors (see below), whose sum is σ = 821736840267. Its totient is φ = 540723414672.

The previous prime is 666651021149. The next prime is 666651021187. The reversal of 666651021169 is 961120156666.

It is a happy number.

The square root of 666651021169 is 816487.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 561682797025 + 104968224144 = 749455^2 + 323988^2 .

It is not a de Polignac number, because 666651021169 - 2³¹ = 664503537521 is a prime.

It is a super-2 number, since 2×666651021169² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is not an unprimeable number, because it can be changed into a prime (666651021139) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 760148959 + ... + 760149835.

Almost surely, 2^666651021169 is an apocalyptic number.

666651021169 is the 816487-th square number.

666651021169 is the 408244-th centered octagonal number.

It is an amenable number.

666651021169 is a deficient number, since it is larger than the sum of its proper divisors (155085819098).

666651021169 is an frugal number, since it uses more digits than its factorization.

666651021169 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1820 (or 903 counting only the distinct ones).

The product of its (nonzero) digits is 699840, while the sum is 49.

Multiplying 666651021169 by its sum of digits (49), we get a square (32665900037281 = 5715409²).

666651021169 divided by its sum of digits (49) gives a square (13605122881 = 116641²).

The spelling of 666651021169 in words is "six hundred sixty-six billion, six hundred fifty-one million, twenty-one thousand, one hundred sixty-nine".