100666721 has 2 divisors, whose sum is σ = 100666722. Its totient is φ = 100666720.

The previous prime is 100666691. The next prime is 100666723. The reversal of 100666721 is 127666001.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 93702400 + 6964321 = 9680^2 + 2639^2 .

It is a cyclic number.

It is not a de Polignac number, because 100666721 - 2¹⁴ = 100650337 is a prime.

Together with 100666723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (100666723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50333360 + 50333361.

It is an arithmetic number, because the mean of its divisors is an integer number (50333361).

Almost surely, 2^100666721 is an apocalyptic number.

It is an amenable number.

100666721 is a deficient number, since it is larger than the sum of its proper divisors (1).

100666721 is an equidigital number, since it uses as much as digits as its factorization.

100666721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 100666721 is about 10033.2806698507. The cubic root of 100666721 is about 465.1881475485.

The spelling of 100666721 in words is "one hundred million, six hundred sixty-six thousand, seven hundred twenty-one".