399421 has 6 divisors (see below), whose sum is σ = 439166. Its totient is φ = 363000.

The previous prime is 399409. The next prime is 399433. The reversal of 399421 is 124993.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (399409) and next prime (399433).

It can be written as a sum of positive squares in only one way, i.e., 290521 + 108900 = 539^2 + 330^2 .

It is not a de Polignac number, because 399421 - 2⁵ = 399389 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 399421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399401) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1530 + ... + 1771.

2³⁹⁹⁴²¹ is an apocalyptic number.

It is an amenable number.

399421 is a deficient number, since it is larger than the sum of its proper divisors (39745).

399421 is a wasteful number, since it uses less digits than its factorization.

399421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3323 (or 3312 counting only the distinct ones).

The product of its digits is 1944, while the sum is 28.

The square root of 399421 is about 631.9976265778. The cubic root of 399421 is about 73.6450619017.

It can be divided in two parts, 399 and 421, that added together give a triangular number (820 = T₄₀).

The spelling of 399421 in words is "three hundred ninety-nine thousand, four hundred twenty-one".