451991 has 4 divisors (see below), whose sum is σ = 475800. Its totient is φ = 428184.

The previous prime is 451987. The next prime is 452009. The reversal of 451991 is 199154.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199154 = 2 ⋅99577.

It is not a de Polignac number, because 451991 - 2² = 451987 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (451901) 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, 11876 + ... + 11913.

It is an arithmetic number, because the mean of its divisors is an integer number (118950).

2⁴⁵¹⁹⁹¹ is an apocalyptic number.

451991 is a deficient number, since it is larger than the sum of its proper divisors (23809).

451991 is a wasteful number, since it uses less digits than its factorization.

451991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23808.

The product of its digits is 1620, while the sum is 29.

The square root of 451991 is about 672.3027591792. The cubic root of 451991 is about 76.7437934199.

The spelling of 451991 in words is "four hundred fifty-one thousand, nine hundred ninety-one".