399665987 has 4 divisors (see below), whose sum is σ = 456761136. Its totient is φ = 342570840.

The previous prime is 399665983. The next prime is 399665993. The reversal of 399665987 is 789566993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 789566993 = 31 ⋅25469903.

It is a cyclic number.

It is not a de Polignac number, because 399665987 - 2² = 399665983 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399665983) 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, 28547564 + ... + 28547577.

It is an arithmetic number, because the mean of its divisors is an integer number (114190284).

Almost surely, 2^399665987 is an apocalyptic number.

399665987 is a deficient number, since it is larger than the sum of its proper divisors (57095149).

399665987 is an equidigital number, since it uses as much as digits as its factorization.

399665987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57095148.

The product of its digits is 22044960, while the sum is 62.

The square root of 399665987 is about 19991.6479310736. The cubic root of 399665987 is about 736.6011568817.

The spelling of 399665987 in words is "three hundred ninety-nine million, six hundred sixty-five thousand, nine hundred eighty-seven".