921391 has 4 divisors (see below), whose sum is σ = 923832. Its totient is φ = 918952.

The previous prime is 921379. The next prime is 921407. The reversal of 921391 is 193129.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 193129 = 151 ⋅1279.

It is a cyclic number.

It is not a de Polignac number, because 921391 - 2¹⁵ = 888623 is a prime.

It is a super-2 number, since 2×921391² = 1697922749762, 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 (921331) 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, 520 + ... + 1453.

It is an arithmetic number, because the mean of its divisors is an integer number (230958).

2⁹²¹³⁹¹ is an apocalyptic number.

921391 is a deficient number, since it is larger than the sum of its proper divisors (2441).

921391 is a wasteful number, since it uses less digits than its factorization.

921391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2440.

The product of its digits is 486, while the sum is 25.

The square root of 921391 is about 959.8911396612. The cubic root of 921391 is about 97.3078750060.

The spelling of 921391 in words is "nine hundred twenty-one thousand, three hundred ninety-one".