399661919 has 2 divisors, whose sum is σ = 399661920. Its totient is φ = 399661918.

The previous prime is 399661897. The next prime is 399661931. The reversal of 399661919 is 919166993.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 399661919 - 2⁸ = 399661663 is a prime.

It is a super-2 number, since 2×399661919² = 319459298997525122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (399663919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199830959 + 199830960.

It is an arithmetic number, because the mean of its divisors is an integer number (199830960).

Almost surely, 2^399661919 is an apocalyptic number.

399661919 is a deficient number, since it is larger than the sum of its proper divisors (1).

399661919 is an equidigital number, since it uses as much as digits as its factorization.

399661919 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 708588, while the sum is 53.

The square root of 399661919 is about 19991.5461883267. The cubic root of 399661919 is about 736.5986577084.

The spelling of 399661919 in words is "three hundred ninety-nine million, six hundred sixty-one thousand, nine hundred nineteen".