666254627515661 has 4 divisors (see below), whose sum is σ = 666545187756732. Its totient is φ = 665964067274592.

The previous prime is 666254627515649. The next prime is 666254627515691. The reversal of 666254627515661 is 166515726452666.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 326343863700100 + 339910763815561 = 18064990^2 + 18436669^2 .

It is a cyclic number.

It is not a de Polignac number, because 666254627515661 - 2⁶ = 666254627515597 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 666254627515591 and 666254627515600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666254627515691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 145280117096 + ... + 145280121681.

It is an arithmetic number, because the mean of its divisors is an integer number (166636296939183).

Almost surely, 2^{666254627515661} is an apocalyptic number.

It is an amenable number.

666254627515661 is a deficient number, since it is larger than the sum of its proper divisors (290560241071).

666254627515661 is a wasteful number, since it uses less digits than its factorization.

666254627515661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290560241070.

The product of its digits is 653184000, while the sum is 68.

The spelling of 666254627515661 in words is "six hundred sixty-six trillion, two hundred fifty-four billion, six hundred twenty-seven million, five hundred fifteen thousand, six hundred sixty-one".