399881621 has 2 divisors, whose sum is σ = 399881622. Its totient is φ = 399881620.

The previous prime is 399881563. The next prime is 399881653. The reversal of 399881621 is 126188993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 335256100 + 64625521 = 18310^2 + 8039^2 .

It is a cyclic number.

It is not a de Polignac number, because 399881621 - 2¹⁰ = 399880597 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (399881921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199940810 + 199940811.

It is an arithmetic number, because the mean of its divisors is an integer number (199940811).

Almost surely, 2^399881621 is an apocalyptic number.

It is an amenable number.

399881621 is a deficient number, since it is larger than the sum of its proper divisors (1).

399881621 is an equidigital number, since it uses as much as digits as its factorization.

399881621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 186624, while the sum is 47.

The square root of 399881621 is about 19997.0403060053. The cubic root of 399881621 is about 736.7336072291.

The spelling of 399881621 in words is "three hundred ninety-nine million, eight hundred eighty-one thousand, six hundred twenty-one".