399536561 has 2 divisors, whose sum is σ = 399536562. Its totient is φ = 399536560.

The previous prime is 399536551. The next prime is 399536563. The reversal of 399536561 is 165635993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 338008225 + 61528336 = 18385^2 + 7844^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-399536561 is a prime.

It is a super-3 number, since 3×399536561³ (a number of 27 digits) contains 333 as substring.

Together with 399536563, 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 (399536563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199768280 + 199768281.

It is an arithmetic number, because the mean of its divisors is an integer number (199768281).

Almost surely, 2^399536561 is an apocalyptic number.

It is an amenable number.

399536561 is a deficient number, since it is larger than the sum of its proper divisors (1).

399536561 is an equidigital number, since it uses as much as digits as its factorization.

399536561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 656100, while the sum is 47.

The square root of 399536561 is about 19988.4106671841. The cubic root of 399536561 is about 736.5216357838.

The spelling of 399536561 in words is "three hundred ninety-nine million, five hundred thirty-six thousand, five hundred sixty-one".