399347621 has 2 divisors, whose sum is σ = 399347622. Its totient is φ = 399347620.

The previous prime is 399347617. The next prime is 399347639. The reversal of 399347621 is 126743993.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 388523521 + 10824100 = 19711^2 + 3290^2 .

It is a cyclic number.

It is not a de Polignac number, because 399347621 - 2² = 399347617 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (399347521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199673810 + 199673811.

It is an arithmetic number, because the mean of its divisors is an integer number (199673811).

Almost surely, 2^399347621 is an apocalyptic number.

It is an amenable number.

399347621 is a deficient number, since it is larger than the sum of its proper divisors (1).

399347621 is an equidigital number, since it uses as much as digits as its factorization.

399347621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 244944, while the sum is 44.

The square root of 399347621 is about 19983.6838695972. The cubic root of 399347621 is about 736.4055176334.

The spelling of 399347621 in words is "three hundred ninety-nine million, three hundred forty-seven thousand, six hundred twenty-one".