666101821 has 8 divisors (see below), whose sum is σ = 830464704. Its totient is φ = 519040320.

The previous prime is 666101819. The next prime is 666101881. The reversal of 666101821 is 128101666.

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 666101821 - 2¹ = 666101819 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 (666101801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4325260 + ... + 4325413.

It is an arithmetic number, because the mean of its divisors is an integer number (103808088).

Almost surely, 2^666101821 is an apocalyptic number.

It is an amenable number.

666101821 is a deficient number, since it is larger than the sum of its proper divisors (164362883).

666101821 is a wasteful number, since it uses less digits than its factorization.

666101821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8650691.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 666101821 is about 25808.9484675374. The cubic root of 666101821 is about 873.3336759544. Note that the first 3 decimals are identical.

The spelling of 666101821 in words is "six hundred sixty-six million, one hundred one thousand, eight hundred twenty-one".