399664981 has 4 divisors (see below), whose sum is σ = 420700000. Its totient is φ = 378629964.

The previous prime is 399664973. The next prime is 399665011. The reversal of 399664981 is 189466993.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 399664981 - 2³ = 399664973 is a prime.

It is a super-2 number, since 2×399664981² = 319464194075460722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399664931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10517481 + ... + 10517518.

It is an arithmetic number, because the mean of its divisors is an integer number (105175000).

Almost surely, 2^399664981 is an apocalyptic number.

It is an amenable number.

399664981 is a deficient number, since it is larger than the sum of its proper divisors (21035019).

399664981 is a wasteful number, since it uses less digits than its factorization.

399664981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21035018.

The product of its digits is 2519424, while the sum is 55.

The square root of 399664981 is about 19991.6227705507. The cubic root of 399664981 is about 736.6005388478.

The spelling of 399664981 in words is "three hundred ninety-nine million, six hundred sixty-four thousand, nine hundred eighty-one".