399559681 has 4 divisors (see below), whose sum is σ = 399615700. Its totient is φ = 399503664.

The previous prime is 399559679. The next prime is 399559697. The reversal of 399559681 is 186955993.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 252301456 + 147258225 = 15884^2 + 12135^2 .

It is a cyclic number.

It is not a de Polignac number, because 399559681 - 2¹ = 399559679 is a prime.

It is a super-2 number, since 2×399559681² = 319295877361643522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399559661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15426 + ... + 32203.

It is an arithmetic number, because the mean of its divisors is an integer number (99903925).

Almost surely, 2^399559681 is an apocalyptic number.

It is an amenable number.

399559681 is a deficient number, since it is larger than the sum of its proper divisors (56019).

399559681 is an equidigital number, since it uses as much as digits as its factorization.

399559681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56018.

The product of its digits is 2624400, while the sum is 55.

The square root of 399559681 is about 19988.9889939436. The cubic root of 399559681 is about 736.5358422866.

The spelling of 399559681 in words is "three hundred ninety-nine million, five hundred fifty-nine thousand, six hundred eighty-one".