391621 has 4 divisors (see below), whose sum is σ = 408672. Its totient is φ = 374572.

The previous prime is 391619. The next prime is 391627. The reversal of 391621 is 126193.

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, and also an emirpimes, since its reverse is a distinct semiprime: 126193 = 53 ⋅2381.

It is a cyclic number.

It is not a de Polignac number, because 391621 - 2¹ = 391619 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

391621 is a modest number, since divided by 621 gives 391 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 391592 and 391601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391627) 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, 8491 + ... + 8536.

It is an arithmetic number, because the mean of its divisors is an integer number (102168).

2³⁹¹⁶²¹ is an apocalyptic number.

It is an amenable number.

391621 is a deficient number, since it is larger than the sum of its proper divisors (17051).

391621 is a wasteful number, since it uses less digits than its factorization.

391621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17050.

The product of its digits is 324, while the sum is 22.

The square root of 391621 is about 625.7962927343. The cubic root of 391621 is about 73.1625202538.

The spelling of 391621 in words is "three hundred ninety-one thousand, six hundred twenty-one".