399517561 has 4 divisors (see below), whose sum is σ = 423018612. Its totient is φ = 376016512.

The previous prime is 399517501. The next prime is 399517577. The reversal of 399517561 is 165715993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165715993 = 191 ⋅867623.

It can be written as a sum of positive squares in 2 ways, for example, as 164968336 + 234549225 = 12844^2 + 15315^2 .

It is a cyclic number.

It is not a de Polignac number, because 399517561 - 2¹⁷ = 399386489 is a prime.

It is a super-2 number, since 2×399517561² = 319228563094777442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399517501) 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, 11750500 + ... + 11750533.

It is an arithmetic number, because the mean of its divisors is an integer number (105754653).

Almost surely, 2^399517561 is an apocalyptic number.

It is an amenable number.

399517561 is a deficient number, since it is larger than the sum of its proper divisors (23501051).

399517561 is a wasteful number, since it uses less digits than its factorization.

399517561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23501050.

The product of its digits is 255150, while the sum is 46.

The square root of 399517561 is about 19987.9353861273. The cubic root of 399517561 is about 736.5099604794.

The spelling of 399517561 in words is "three hundred ninety-nine million, five hundred seventeen thousand, five hundred sixty-one".