660110021 has 2 divisors, whose sum is σ = 660110022. Its totient is φ = 660110020.

The previous prime is 660109999. The next prime is 660110023. The reversal of 660110021 is 120011066.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 341880100 + 318229921 = 18490^2 + 17839^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-660110021 is a prime.

It is a Sophie Germain prime.

Together with 660110023, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (660110023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330055010 + 330055011.

It is an arithmetic number, because the mean of its divisors is an integer number (330055011).

Almost surely, 2^660110021 is an apocalyptic number.

It is an amenable number.

660110021 is a deficient number, since it is larger than the sum of its proper divisors (1).

660110021 is an equidigital number, since it uses as much as digits as its factorization.

660110021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 660110021 is about 25692.6063489090. The cubic root of 660110021 is about 870.7071455952.

Adding to 660110021 its reverse (120011066), we get a palindrome (780121087).

The spelling of 660110021 in words is "six hundred sixty million, one hundred ten thousand, twenty-one".