1991451 has 32 divisors (see below), whose sum is σ = 3414528. Its totient is φ = 1002240.

The previous prime is 1991449. The next prime is 1991461. The reversal of 1991451 is 1541991.

It is not a de Polignac number, because 1991451 - 2¹ = 1991449 is a prime.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (1991461) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8431 + ... + 8663.

It is an arithmetic number, because the mean of its divisors is an integer number (106704).

2^1991451 is an apocalyptic number.

1991451 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1991451 is a deficient number, since it is larger than the sum of its proper divisors (1423077).

1991451 is a wasteful number, since it uses less digits than its factorization.

1991451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291.

The product of its digits is 1620, while the sum is 30.

The square root of 1991451 is about 1411.1877975663. The cubic root of 1991451 is about 125.8123308465.

It can be divided in two parts, 1991 and 451, that added together give a palindrome (2442).

The spelling of 1991451 in words is "one million, nine hundred ninety-one thousand, four hundred fifty-one".