345991 has 4 divisors (see below), whose sum is σ = 357184. Its totient is φ = 334800.

The previous prime is 345979. The next prime is 345997. The reversal of 345991 is 199543.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199543 = 383 ⋅521.

It is not a de Polignac number, because 345991 - 2⁹ = 345479 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 11161 = 345991 / (3 + 4 + 5 + 9 + 9 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (345997) 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, 5550 + ... + 5611.

It is an arithmetic number, because the mean of its divisors is an integer number (89296).

2³⁴⁵⁹⁹¹ is an apocalyptic number.

345991 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

345991 is a deficient number, since it is larger than the sum of its proper divisors (11193).

345991 is a wasteful number, since it uses less digits than its factorization.

345991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11192.

The product of its digits is 4860, while the sum is 31.

The square root of 345991 is about 588.2099965149. The cubic root of 345991 is about 70.2028808108.

The spelling of 345991 in words is "three hundred forty-five thousand, nine hundred ninety-one".