399661217 has 2 divisors, whose sum is σ = 399661218. Its totient is φ = 399661216.

The previous prime is 399661187. The next prime is 399661247. The reversal of 399661217 is 712166993.

It is a balanced prime because it is at equal distance from previous prime (399661187) and next prime (399661247).

It can be written as a sum of positive squares in only one way, i.e., 397444096 + 2217121 = 19936^2 + 1489^2 .

It is a cyclic number.

It is not a de Polignac number, because 399661217 - 2¹⁶ = 399595681 is a prime.

It is not a weakly prime, because it can be changed into another prime (399661247) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199830608 + 199830609.

It is an arithmetic number, because the mean of its divisors is an integer number (199830609).

Almost surely, 2^399661217 is an apocalyptic number.

It is an amenable number.

399661217 is a deficient number, since it is larger than the sum of its proper divisors (1).

399661217 is an equidigital number, since it uses as much as digits as its factorization.

399661217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 122472, while the sum is 44.

The square root of 399661217 is about 19991.5286308976. The cubic root of 399661217 is about 736.5982264334.

The spelling of 399661217 in words is "three hundred ninety-nine million, six hundred sixty-one thousand, two hundred seventeen".