660021997 has 2 divisors, whose sum is σ = 660021998. Its totient is φ = 660021996.

The previous prime is 660021983. The next prime is 660022079. The reversal of 660021997 is 799120066.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 622702116 + 37319881 = 24954^2 + 6109^2 .

It is a cyclic number.

It is not a de Polignac number, because 660021997 - 2¹⁵ = 659989229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (660021917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330010998 + 330010999.

It is an arithmetic number, because the mean of its divisors is an integer number (330010999).

Almost surely, 2^660021997 is an apocalyptic number.

It is an amenable number.

660021997 is a deficient number, since it is larger than the sum of its proper divisors (1).

660021997 is an equidigital number, since it uses as much as digits as its factorization.

660021997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40824, while the sum is 40.

The square root of 660021997 is about 25690.8932697950. The cubic root of 660021997 is about 870.6684416770.

The spelling of 660021997 in words is "six hundred sixty million, twenty-one thousand, nine hundred ninety-seven".